The JWST Discovery of the Triply-imaged Type Ia “Supernova H0pe” and Observat...Sérgio Sacani
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared
Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–
2 kpc from its host galaxy Arc 2 and appears in three different locations as a result of gravitational
lensing by G165. These data can yield a value for Hubble’s constant using time delays from this
multiply-imaged SN Ia that we call “SN H0pe.” Over the entire field we identified 21 image multiplicities,
confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new
lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014M⊙. The photometry uncovered
a galaxy overdensity at Arc 2’s redshift. NIRSpec confirmed six member galaxies, four of which
surround Arc 2 with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. Arc 2
dominates the stellar mass ((5.0±0.1)×1011M⊙), which is a factor of ten higher than other members
of this compact galaxy group. These other group members have specific star formation rates (sSFR)
arXiv:2309.07326v1 [astro-ph.GA] 13 Sep 2023
2 Frye, Pascale, Pierel et al.
of 2–260 Gyr−1 derived from the Hα-line flux corrected for stellar absorption, dust extinction, and slit
losses. Another group centered on the dusty star forming galaxy Arc 1 is at z = 2.24. The total SFR
for the Arc 1 group (≳400M⊙ yr−1) translates to a supernova rate of ∼1 SNe yr−1, suggesting that
regular monitoring of this cluster may yield additional SNe.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Three Ultra-...Sérgio Sacani
We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby
spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in
the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs
and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data
reach 3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances,
structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations
(age ∼12 Gyr, [M/H] −1.5) and have sizes (rh ∼ 110–3000 pc) and luminosities (MV ∼ −7 to −12 mag) largely
consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered
beyond the Local Group. We also use archival H I data to place limits on the gas content of our discoveries. Deep
imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity
function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
Artigo descreve estudo feitos pelos astrônomos utilizando o ALMA para descobrir um proto-aglomerado globular de estrelas gigantes se formando no interior das galáxias Antenas, o famoso par de galáxias em interação. É a primeira vez que os astrônomos conseguem observar um objeto desse tipo nos seus estágios iniciais de vida e com o ambiente ao redor inalterado.
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
The JWST Discovery of the Triply-imaged Type Ia “Supernova H0pe” and Observat...Sérgio Sacani
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared
Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–
2 kpc from its host galaxy Arc 2 and appears in three different locations as a result of gravitational
lensing by G165. These data can yield a value for Hubble’s constant using time delays from this
multiply-imaged SN Ia that we call “SN H0pe.” Over the entire field we identified 21 image multiplicities,
confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new
lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014M⊙. The photometry uncovered
a galaxy overdensity at Arc 2’s redshift. NIRSpec confirmed six member galaxies, four of which
surround Arc 2 with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. Arc 2
dominates the stellar mass ((5.0±0.1)×1011M⊙), which is a factor of ten higher than other members
of this compact galaxy group. These other group members have specific star formation rates (sSFR)
arXiv:2309.07326v1 [astro-ph.GA] 13 Sep 2023
2 Frye, Pascale, Pierel et al.
of 2–260 Gyr−1 derived from the Hα-line flux corrected for stellar absorption, dust extinction, and slit
losses. Another group centered on the dusty star forming galaxy Arc 1 is at z = 2.24. The total SFR
for the Arc 1 group (≳400M⊙ yr−1) translates to a supernova rate of ∼1 SNe yr−1, suggesting that
regular monitoring of this cluster may yield additional SNe.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Three Ultra-...Sérgio Sacani
We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby
spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in
the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs
and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data
reach 3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances,
structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations
(age ∼12 Gyr, [M/H] −1.5) and have sizes (rh ∼ 110–3000 pc) and luminosities (MV ∼ −7 to −12 mag) largely
consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered
beyond the Local Group. We also use archival H I data to place limits on the gas content of our discoveries. Deep
imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity
function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
Artigo descreve estudo feitos pelos astrônomos utilizando o ALMA para descobrir um proto-aglomerado globular de estrelas gigantes se formando no interior das galáxias Antenas, o famoso par de galáxias em interação. É a primeira vez que os astrônomos conseguem observar um objeto desse tipo nos seus estágios iniciais de vida e com o ambiente ao redor inalterado.
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
The massive relic galaxy NGC 1277 is dark matter deficient From dynamical mod...Sérgio Sacani
According to the Λ cold dark matter (ΛCDM) cosmology, present-day galaxies with stellar masses M? > 1011 M should contain
a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M? ≈
1.5 × 1011 M, dark matter should account for ∼15% of the dynamical mass within one effective radius (1 Re) and for ∼60% within
5 Re
. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the
accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called
relic galaxies, are thought to be the frozen remains of the massive ETG population at z & 2. The best relic galaxy candidate discovered
to date is NGC 1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to
revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to 5 Re). By using Jeans anisotropic modelling, we find
a negligible dark matter fraction within 5 Re (fDM(5 Re) < 0.05; two-sigma confidence level), which is in tension with the ΛCDM
expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we
propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the
framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted
within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments,
where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ≈2000 km s−1
required for the
latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
The Possible Tidal Demise of Kepler’s First Planetary SystemSérgio Sacani
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet
(1.1RJ, 5.9MJ) orbiting an evolved host star (2.9Re, 1.5Me). Using transit timing measurements from Kepler,
Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate = -
+ P 131 22
20 ms yr−1
, corresponding to an infall timescale P P » 2.5 Myr. We consider other explanations for the
data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed
period derivative implies a tidal quality factor
¢ = ´ -
+ Q 2.50 10 0.62
0.85 4, in good agreement with theoretical
predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire
inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for
the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new
benchmark for understanding tidal physics at the end of the planetary life cycle
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
Is Betelgeuse Really Rotating? Synthetic ALMA Observations of Large-scale Con...Sérgio Sacani
The evolved stages of massive stars are poorly understood, but invaluable constraints can be derived from spatially resolved observations of nearby red supergiants, such as Betelgeuse. Atacama Large Millimeter/submillimeter Array (ALMA) observations of Betelgeuse showing a dipolar velocity field have been interpreted as evidence for a projected rotation rate of about 5 km s−1. This is 2 orders of magnitude larger than predicted by single-star evolution, which led to suggestions that Betelgeuse is a binary merger. We propose instead that large-scale convective motions can mimic rotation, especially if they are only partially resolved. We support this claim with 3D CO5BOLDsimulations of nonrotating red supergiants that we postprocessed to predict ALMA images and SiO spectra. We show that our synthetic radial velocity maps have a 90% chance of being falsely interpreted as evidence for a projected rotation rate of 2 km s−1 or larger for our fiducial simulation. We conclude that we need at least another ALMA observation to firmly establish whether Betelgeuse is indeed rapidly rotating. Such observations would also provide insight into the role of angular momentum and binary interaction in the late evolutionary stages. The data will further probe the structure and complex physical processes in the atmospheres of red supergiants, which are immediate progenitors of supernovae and are believed to be essential in the formation of gravitational-wave sources.
JWST early Universe observations and 𝚲CDM cosmologySérgio Sacani
Deep space observations of the James Webb Space Telescope (JWST) have revealed that the structure and
masses of very early Universe galaxies at high redshifts (𝑧~15), existing at ~0.3 Gyr after the BigBang,
may be as evolved as the galaxies in existence for ~10 Gyr. The JWST findings are thus in strong tension
with the ΛCDM cosmological model. While tired light (TL) models have been shown to comply with the
JWST angular galaxy size data, they cannot satisfactorily explain isotropy of the cosmic microwave
background (CMB) observations or fit the supernovae distance modulus vs. redshift data well. We have
developed hybrid models that include the tired light concept in the expanding universe. The hybrid ΛCDM
model fits the supernovae type 1a data well but not the JWST observations. We present a model with
covarying coupling constants (CCC), starting from the modified FLRW metric and resulting Einstein and
Friedmann equations, and a CCC+TL hybrid model. They fit the Pantheon+ data admirably, and the
CCC+TL model is compliant with the JWST observations. It stretches the age of the universe to 26.7 Gyr
with 5.8 Gyr at 𝑧 = 10 and 3.5 Gyr at 𝑧 = 20, giving enough time to form massive galaxies. It thus
resolves the 'impossible early galaxy' problem without requiring the existence of primordial black hole
seeds or modified power spectrum, rapid formation of massive population III stars, and super Eddington
accretion rates. One could infer the CCC model as an extension of the ΛCDM model with a dynamic
cosmological constant.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Star formation at the smallest scales; A JWST study of the clump populations ...Sérgio Sacani
We present the clump populations detected in 18 lensed galaxies at redshifts 1 to 8.5 within the lensing cluster field SMACS0723.
The recent JWST Early Release Observations of this poorly known region of the sky have revealed numerous point-like sources
within and surrounding their host galaxies, undetected in the shallower HST images. We use JWST multiband photometry and
the lensing model of this galaxy cluster to estimate the intrinsic sizes and magnitudes of the stellar clumps. We derive optical
restframe effective radii from <10 to hundreds pc and masses ranging from ∼ 105
to 109 M, overlapping with massive star
clusters in the local universe. Clump ages range from 1 Myr to 1 Gyr. We compare the crossing time to the age of the clumps
and determine that between 45 and 60 % of the detected clumps are consistent with being gravitationally bound. On average,
the dearth of Gyr old clumps suggests that the dissolution time scales are shorter than 1 Gyr. We see a significant increase in the
luminosity (mass) surface density of the clumps with redshift. Clumps in reionisation era galaxies have stellar densities higher
than star clusters in the local universe. We zoom in into single galaxies at redshift < 6 and find for two galaxies, the Sparkler and
the Firework, that their star clusters/clumps show distinctive colour distributions and location surrounding their host galaxy that
are compatible with being accredited or formed during merger events. The ages of some of the compact clusters are between
1 and 4 Gyr, e.g., globular cluster precursors formed around 9-12 Gyr ago. Our study, conducted on a small sample of galaxies,
shows the potential of JWST observations for understanding the conditions under which star clusters form in rapidly evolving
galaxies.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
More Related Content
Similar to The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWST
The massive relic galaxy NGC 1277 is dark matter deficient From dynamical mod...Sérgio Sacani
According to the Λ cold dark matter (ΛCDM) cosmology, present-day galaxies with stellar masses M? > 1011 M should contain
a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M? ≈
1.5 × 1011 M, dark matter should account for ∼15% of the dynamical mass within one effective radius (1 Re) and for ∼60% within
5 Re
. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the
accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called
relic galaxies, are thought to be the frozen remains of the massive ETG population at z & 2. The best relic galaxy candidate discovered
to date is NGC 1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to
revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to 5 Re). By using Jeans anisotropic modelling, we find
a negligible dark matter fraction within 5 Re (fDM(5 Re) < 0.05; two-sigma confidence level), which is in tension with the ΛCDM
expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we
propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the
framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted
within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments,
where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ≈2000 km s−1
required for the
latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
The Possible Tidal Demise of Kepler’s First Planetary SystemSérgio Sacani
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet
(1.1RJ, 5.9MJ) orbiting an evolved host star (2.9Re, 1.5Me). Using transit timing measurements from Kepler,
Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate = -
+ P 131 22
20 ms yr−1
, corresponding to an infall timescale P P » 2.5 Myr. We consider other explanations for the
data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed
period derivative implies a tidal quality factor
¢ = ´ -
+ Q 2.50 10 0.62
0.85 4, in good agreement with theoretical
predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire
inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for
the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new
benchmark for understanding tidal physics at the end of the planetary life cycle
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
Is Betelgeuse Really Rotating? Synthetic ALMA Observations of Large-scale Con...Sérgio Sacani
The evolved stages of massive stars are poorly understood, but invaluable constraints can be derived from spatially resolved observations of nearby red supergiants, such as Betelgeuse. Atacama Large Millimeter/submillimeter Array (ALMA) observations of Betelgeuse showing a dipolar velocity field have been interpreted as evidence for a projected rotation rate of about 5 km s−1. This is 2 orders of magnitude larger than predicted by single-star evolution, which led to suggestions that Betelgeuse is a binary merger. We propose instead that large-scale convective motions can mimic rotation, especially if they are only partially resolved. We support this claim with 3D CO5BOLDsimulations of nonrotating red supergiants that we postprocessed to predict ALMA images and SiO spectra. We show that our synthetic radial velocity maps have a 90% chance of being falsely interpreted as evidence for a projected rotation rate of 2 km s−1 or larger for our fiducial simulation. We conclude that we need at least another ALMA observation to firmly establish whether Betelgeuse is indeed rapidly rotating. Such observations would also provide insight into the role of angular momentum and binary interaction in the late evolutionary stages. The data will further probe the structure and complex physical processes in the atmospheres of red supergiants, which are immediate progenitors of supernovae and are believed to be essential in the formation of gravitational-wave sources.
JWST early Universe observations and 𝚲CDM cosmologySérgio Sacani
Deep space observations of the James Webb Space Telescope (JWST) have revealed that the structure and
masses of very early Universe galaxies at high redshifts (𝑧~15), existing at ~0.3 Gyr after the BigBang,
may be as evolved as the galaxies in existence for ~10 Gyr. The JWST findings are thus in strong tension
with the ΛCDM cosmological model. While tired light (TL) models have been shown to comply with the
JWST angular galaxy size data, they cannot satisfactorily explain isotropy of the cosmic microwave
background (CMB) observations or fit the supernovae distance modulus vs. redshift data well. We have
developed hybrid models that include the tired light concept in the expanding universe. The hybrid ΛCDM
model fits the supernovae type 1a data well but not the JWST observations. We present a model with
covarying coupling constants (CCC), starting from the modified FLRW metric and resulting Einstein and
Friedmann equations, and a CCC+TL hybrid model. They fit the Pantheon+ data admirably, and the
CCC+TL model is compliant with the JWST observations. It stretches the age of the universe to 26.7 Gyr
with 5.8 Gyr at 𝑧 = 10 and 3.5 Gyr at 𝑧 = 20, giving enough time to form massive galaxies. It thus
resolves the 'impossible early galaxy' problem without requiring the existence of primordial black hole
seeds or modified power spectrum, rapid formation of massive population III stars, and super Eddington
accretion rates. One could infer the CCC model as an extension of the ΛCDM model with a dynamic
cosmological constant.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Star formation at the smallest scales; A JWST study of the clump populations ...Sérgio Sacani
We present the clump populations detected in 18 lensed galaxies at redshifts 1 to 8.5 within the lensing cluster field SMACS0723.
The recent JWST Early Release Observations of this poorly known region of the sky have revealed numerous point-like sources
within and surrounding their host galaxies, undetected in the shallower HST images. We use JWST multiband photometry and
the lensing model of this galaxy cluster to estimate the intrinsic sizes and magnitudes of the stellar clumps. We derive optical
restframe effective radii from <10 to hundreds pc and masses ranging from ∼ 105
to 109 M, overlapping with massive star
clusters in the local universe. Clump ages range from 1 Myr to 1 Gyr. We compare the crossing time to the age of the clumps
and determine that between 45 and 60 % of the detected clumps are consistent with being gravitationally bound. On average,
the dearth of Gyr old clumps suggests that the dissolution time scales are shorter than 1 Gyr. We see a significant increase in the
luminosity (mass) surface density of the clumps with redshift. Clumps in reionisation era galaxies have stellar densities higher
than star clusters in the local universe. We zoom in into single galaxies at redshift < 6 and find for two galaxies, the Sparkler and
the Firework, that their star clusters/clumps show distinctive colour distributions and location surrounding their host galaxy that
are compatible with being accredited or formed during merger events. The ages of some of the compact clusters are between
1 and 4 Gyr, e.g., globular cluster precursors formed around 9-12 Gyr ago. Our study, conducted on a small sample of galaxies,
shows the potential of JWST observations for understanding the conditions under which star clusters form in rapidly evolving
galaxies.
Similar to The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWST (20)
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Efficient spin-up of Earth System Models usingsequence accelerationSérgio Sacani
Marine and terrestrial biogeochemical models are key components of the Earth System Models (ESMs) used toproject future environmental changes. However, their slow adjustment time also hinders effective use of ESMsbecause of the enormous computational resources required to integrate them to a pre-industrial equilibrium. Here,a solution to this "spin-up" problem based on "sequence acceleration", is shown to accelerate equilibration of state-of-the-art marine biogeochemical models by over an order of magnitude. The technique can be applied in a "blackbox" fashion to existing models. Even under the challenging spin-up protocols used for Intergovernmental Panelon Climate Change (IPCC) simulations, this algorithm is 5 times faster. Preliminary results suggest that terrestrialmodels can be similarly accelerated, enabling a quantification of major parametric uncertainties in ESMs, improvedestimates of metrics such as climate sensitivity, and higher model resolution than currently feasible.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Toxic effects of heavy metals : Lead and Arsenicsanjana502982
Heavy metals are naturally occuring metallic chemical elements that have relatively high density, and are toxic at even low concentrations. All toxic metals are termed as heavy metals irrespective of their atomic mass and density, eg. arsenic, lead, mercury, cadmium, thallium, chromium, etc.
2. globular clusters with young stellar populations seen in nearby
starbursting and merging galaxies (Schweizer & Seitzer 1998;
de Grijs et al. 2001). In this case, globular cluster formation
might be a natural product of continuous galaxy evolution in
systems with high gas fractions, and globular cluster formation
would peak at lower redshifts (Trujillo-Gomez et al. 2021).
We are on the cusp of distinguishing observationally
between these two globular cluster formation channels. JWST
is capable of observing routinely down to nJy flux levels at
wavelengths beyond two microns, and thus of observing
globular cluster formation occurring at high redshift
(Carlberg 2002; Renzini 2017; Vanzella et al. 2017, 2022).
In this paper, we use newly released data from JWST to analyse
the nature of the point sources seen around a remarkable
multiply imaged galaxy at z = 1.378 that we fondly named the
“Sparkler”. One image of this galaxy is strongly magnified by a
factor of ∼10–100 (Caminha et al. 2022; Mahler et al. 2022) by
the z = 0.39 galaxy cluster SMACS J0723.37327 (hereafter
SMACS0723). Our goal is to determine whether these point
sources are (1) globular clusters, (2) super star clusters in the
body of the galaxy, or (3) the product of global star formation
in this galaxy being driven by some other mechanism.
Throughout this paper we use AB magnitudes and assume a flat
cosmology with Ωm = 0.3, ΩΛ = 0.7 and H0 = 70 km s−1
Mpc−1
.
2. Data
The imaging and wide-field slitless spectroscopy data used
for this work are from the JWST Early Release Observations
(ERO) program 2736 (“Webb’s First Deep Field”; Pontoppidan
et al. 2022). The galaxy cluster was observed with all four
instruments on JWST. Only Near-Infrared Camera (NIRCam;
Rieke et al. 2005) imaging and Near-Infrared Imager and
Slitless Spectrograph (NIRISS; Doyon et al. 2012) spectrosc-
opy are used in this paper. NIRCam imaging is available in six
broadband filters: F090W, F150W, F200W, F277W, F356W,
and F444W. Shallow NIRISS wide-field spectroscopy was
obtained in the F115W and F200W filters with the two
orthogonal low-resolution grisms to mitigate contamination
(Willott et al. 2022). Only the F115W grism data are used in
this study, because they were taken with the only filter
containing a strong emission line, [OIII] λ5007. These JWST
data are supplemented with Hubble Space Telescope (HST)
Advanced Camera for Surveys (ACS) imaging in F435W and
F606W from the RELICS program, drizzled to the same pixel
grid (Coe et al. 2019).
We reduced all imaging and slitless spectroscopic data
together using the grism redshift and line analysis software for
space-based spectroscopy package Grizli15
(Brammer &
Matharu 2021). We first obtained uncalibrated ramp exposures
from the Mikulski Archive for Space Telescopes (MAST16
),
and ran a modified version of the JWST pipeline stage
Detector1, which makes detector-level corrections for, e.g.,
ramp fitting, cosmic ray rejection (including extra “snowball”
artifact flagging), dark current, and calculates “rate images”.
Our modified version of the pipeline also includes a column-
average correction for 1/f-noise. Subsequently, we used the
preprocessing routines in Grizli to align all of the exposures
to the HST images, subtracted the sky background, and
drizzled all images to a common pixel grid with a scale of 0 04
per pixel. For the NIRCam F090W, F150W, and F200W
images we created another data product with a 0 02 pixel
scale. The context for the JWST Operational Pipeline
(CRDS_CTX) used for reducing the NIRISS (NIRCam) data
was jwst_0932.pmap (jwst_0916.pmap). This is a
preflight version of the NIRCam reference files, so the
NIRCam fluxes should be treated with caution. One conse-
quence of this is that the NIRCam photometric zero points
calculated from our reductions may be incorrect for in-flight
performance, so we used EAZY (Brammer et al. 2008) to derive
zero-point offsets consistent with photometric redshift fitting of
the full source catalog. Bright cluster galaxies and the
intracluster light were modeled and subtracted out using a
custom code (N. Martis et al., in preparation). To enable
measurement of accurate colors our analysis was done after
convolution by a kernel to match the point-spread function
(PSF) of F444W.
Figure 1 shows images of the Sparkler. The coordinates for
the three images of the background galaxy are presented in the
caption accompanying the figure. The Sparkler was first
identified as multiply imaged in HST imaging combined with
ESO MUSE integral-field spectroscopy that shows all three
images having [OII] λ3727 emission (Golubchik et al. 2022).
We adopt the spectroscopic redshift of z = 1.378 ± 0.001
obtained from the MUSE [OII] λ3727 line (Caminha et al.
2022; Golubchik et al. 2022; Mahler et al. 2022). The
magnifications of the three images (labeled as 1, 2, and 3 in
Figure 1) in the lensing model of Mahler et al. (2022; their IDs
2.1, 2.2, and 2.3) are 3.6 ± 0.1, 14.9 ± 0.8, and 3.0 ± 0.1,
respectively. In the lensing model of Caminha et al. (2022; their
IDs 3a, 3b, and 3c) the magnifications are significantly higher:
9.2 , 103 ,
1.2
1.3
47
153
-
+
-
+
and 6.1 0.7
0.7
-
+
, respectively. Based on the
measured flux ratios between the three images we consider
the Caminha et al. (2022) model to fit the properties of this
galaxy better. As shown in Figure 1, there may be critical
curves and/or high-magnification contours crossing image 2 (a
magnification of 5–10 in the Mahler et al. 2022 model and a
magnification of 30–100+ in the Caminha et al. 2022 model),
suggesting strong differential magnification in the image.
Figure 2 shows a multiband montage of image 2 of the
Sparkler, using data from HST/ACS, HST/WFC3, and
JWST/NIRCam short- and long-wavelength cameras at
observed wavelengths spanning 0.4–4.4 μm. Circles in the
lower-left of each panel show the FWHM of the PSF which
range from 0 034 for NIRCam/F150W to 0 145 for
NIRCam/F444W.17
The exquisite resolution of JWST/NIR-
Cam’s short wavelength data best reveals the compact sources
surrounding the galaxy, which were not resolved by HST in
earlier observations, even at similar wavelengths.
3. Methods
In this letter we focus our attention on twelve compact
candidates in and around image 2 of the Sparkler, at least seven
of which are confirmed to be unique from image 1. In this
preliminary exploration, we selected candidates by eye,
focusing mainly on compact objects (“sparkles”) in unconta-
minated regions of the image. A few compact sources in the
galaxy itself were also added to our sample to allow us to
compare objects in the body of the Sparkler to objects in the
periphery of the galaxy. Objects were selected using the very
15
https://github.com/gbrammer/grizli
16
https://archive.stsci.edu/ 17
JWST User Documentation
2
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
3. deep 0 02 pixel scale F150W image, and were chosen to be
broadly representative of the compact sources in this system.
As described below, 2D modeling confirms that the objects
chosen are unresolved. We emphasize that the objects analysed
in this letter are not a complete sample, and as the main galaxy
is close to (though likely outside) a fold caustic, it is also
possible that some of the sparkles are multiple images of each
other. Construction of a complete sample and their stellar mass
surface densities will require detailed background subtraction
and foreground galaxy lens modeling, which is deferred to a
future paper.
3.1. Aperture Photometry
Photometry is challenging in crowded fields, and in the case
of the Sparkler the challenges are compounded by contamina-
tion from the host galaxy and from other nearby sources. This
contamination can significantly alter the shape of the SED of
the individual compact sources. In a future paper we will
present a full catalog of compact sources around the Sparkler
that attempts to account for these effects by subtracting
contamination models and using PSF photometry. For
simplicity and robustness, in the present paper we used
aperture photometry, as this technique is relatively insensitive
to variations in the local background. Photometry was done
using images that (1) are on 0 04 pixel scale, (2) have a bright
cluster galaxy and intracluster light-subtracted, and (3) are
F444W PSF-convolved F435W, F606W, F090W, F150W,
F200W, F277W, F356W, and F444W images.
Using photutils (Bradley et al. 2021), circular apertures
with radii of 0 12, 0 16, and 0 20 were defined using the
centroided positions of the twelve sparkles in the F150W
image. An annulus starting at the edge of the aperture and with
a width of 0 08 was used to estimate the median local
background, which was subtracted from the aperture flux.
Aperture correction was applied by multiplying by the F444W
PSF growth curve. To determine contamination corrections, we
injected simulated point sources of various fluxes around the
galaxy to determine how well our procedure recovered the
intrinsic total flux of the compact sources. We found that the
precision of the photometry varied widely across the different
filters, environments, and intrinsic brightnesses of the sources,
but that these variations could be quantified by simulations. For
every sparkle, we identified a location proximate to it in which
we injected simulated point sources to model the measurement
accuracy. For a sparkle at a given wavelength, we injected 20
point sources of total flux varying between 0.1 and 10 times the
measured flux of the source and measured their fluxes using the
same techniques used to analyse the original sources. We then
fit the intrinsic flux as a function of the measured flux with a
second-order polynomial, which we used to determine local
aperture corrections. This process was repeated across 20
different locations around the galaxy to estimate the uncertainty
in the flux measurement. We selected the 0 20 aperture for our
final photometry as the corrected flux recovered >99% of the
intrinsic flux across all environments. The procedure was
performed for all twelve sparkles in all eight filters to construct
the final SED of the sources. For sources that are undetected,
Figure 1. Color images of the Sparkler and its environs made by combining F090W, F150W, and F200W images at native spatial resolution. The left panel shows the
region around the three images of the Sparkler, with lines of lensing magnification from the Mahler et al. (2022; solid curves) and Caminha et al. (2022; dashed curves)
models overlaid. Note that regions of very strong magnification (μ ∼ 10–100) cross image 2 of the Sparkler. The remaining three panels zoom in on the three images
of this galaxy. Images are centered on the following positions. Image 1: R.A. = 110.83846, decl. = −73.45102; image 2: R.A. = 110.84051, decl. = −73.45487; and
image 3: R.A. = 110.83614, decl. = −73.45879. Note the compact sources, many of them red, surrounding the body of the galaxy; these are most prominent in image
2, but are also discernible in images 1 and 3.
3
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
4. we assigned an upper limit of three times the noise of the
image.
3.2. SED Fitting and Estimating the Physical Properties
Spectral energy distributions (SEDs) derived from our
aperture photometry were analysed using the DENSE BASIS
method18
(Iyer & Gawiser 2017; Iyer et al. 2019) to determine
nonparametric star formation histories (SFHs), masses, ages,
metallicities, and dust extinction values for our compact
sources. The DENSE BASIS fits were run with a single t50
parameter, following the prescription of Iyer et al. (2019), with
the full methodology and validation tests presented by Iyer
et al. (2018, 2019) and Olsen et al. (2021). The primary
advantages of using nonparametric SFHs is that they allow us
to account for multiple stellar populations, robustly derive
SFH-related quantities including masses, star formation rates
(SFRs), and ages, and allow us to set explicit priors in SFH
space to prevent outshining due to younger stellar populations
that could otherwise bias the estimates of these properties (Iyer
& Gawiser 2017; Leja et al. 2019; Lower et al. 2020).
However, DENSE BASIS, by design, implements correlated
SFRs over time, to encode the effects of physical processes in
galaxies that regulate star formation better, and to recover
complex SFHs containing multiple stellar populations better
(Iyer et al. 2019). The formalism smooths out SFHs that are
instantaneous pulses, and has an age resolution of about
0.5 Gyr. We therefore also undertook SED fits based on simple
luminosity evolution of simple stellar populations (SSPs). As
will be seen below, in several cases the DENSE BASIS fit results
return SFHs that are as close to instantaneous pulses as the
method allows. In such cases, the SSP fits may give
comparably good results with fewer assumptions. SSP fits also
have the benefit of returning unambiguously defined ages.
Since the DENSE BASIS fits provide a full SFH posterior, we
will define the “age” from these fits to be the time at which the
SFR peaks (tpeak). Using validation tests fitting synthetic SSP
sources injected into the field and mock photometry with
similar noise properties to the observed sources, we find that
this can robustly recover the age of the corresponding SSP
within uncertainties, finding a bias and scatter of
, 0.15, 1.00
t50
( ) ( )
m s º Gyr, , 0.13, 0.86
tpeak
( ) ( )
m s º Gyr,
and , 0.20, 0.86
ageSSP
( ) ( )
m s º - Gyr for the three metrics
tested.
3.3. Grism Extraction and Fitting
Before extracting the individual NIRISS spectra, we
constructed a contamination model of the entire field using
Grizli. We modeled the sources at both grism orientations.
This model was built using a segmentation map and
photometric catalog created with SEP (Barbary 2016; Bertin
& Arnouts 1996). We initially assumed a flat spectrum,
normalized by the flux in the photometric catalog, in our
models. Successive higher-order polynomials were then fit to
each source, iteratively, until the residuals in the global
contamination model were negligible.
After the spectral modeling of the full field for contamination
removal, we then extracted the 2D grism cutouts of the three
images of the Sparkler and fitted their spectra using the
Grizli redshift-fitting routine with a set of FSPS and
emission-line templates. Grizli forward modeled the 1D
spectral template set to the 2D grism frames based on the
source morphologies in the direct imaging. Grizli identified
a redshift solution for the Sparkler based on the identification of
[OIII] λ5007 at 1.2 μm in the F115W grism data. This is
consistent with the identification of the complementary [OII]
λ3727 line previously reported in the MUSE data, and securely
confirms the spectroscopic redshift of the source as z = 1.38.
As a product of the fitting, emission-line maps of the [OIII]
λ5007 line were created for the three images of the Sparkler.
4. Results
The fluxes and associated uncertainties for the twelve
compact sources (sparkles) in and around the Sparkler are
presented in Table 1, and their positions are identified in image
2 of the Sparkler in the middle row of panel (a) in Figure 3.
Panel (b) of this figure shows point source fits (using GALFIT;
Peng et al. 2010) to several sparkles in our sample. Residuals
from the fits are negligible, confirming the original visual
impression that these compact sources are unresolved. Panel (c)
in Figure 3 shows the colors of the individual sparkles in the
rest-frame urJ color–color space (measured directly from
Figure 2. Image 2 of the Sparkler from HST/ACS, HST/WFC3, and JWST/NIRCam short wavelength (SW) and long wavelength (LW) at observed wavelengths
from 0.4 to 4.4 μm. Circles in the lower-left of each panel show the FWHM of the PSF which ranges from 0 034 to NIRCam/F150W to 0 145 for NIRCam/F444W.
Note the exquisite resolution of JWST/NIRCamSW, which reveals the compact sources surrounding the galaxy, which were not resolved by HST in earlier
observations at similar wavelengths.
18
https://dense-basis.readthedocs.io/
4
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
5. F090W, F200W, and the average of the F277W and F356W
fluxes), overplotted on the distribution of z ∼ 1.4 galaxies from
the COSMOS2020 catalog (Weaver et al. 2022). The body of
the Sparkler galaxy (blue point) is in the star-forming blue
cloud, as are 7 of 12 of our sparkles (orange points). However,
five of the sparkles have red colors (u*
− r > 1.5) consistent
with those of quiescent systems (so-called red clouds). These
five red, unresolved objects will constitute our sample of
globular cluster candidates throughout this paper, and are color-
coded in pink in all figures in this paper.
The SEDs and derived SFHs inferred from our modeling are
shown in Figure 4. The physical properties corresponding to
the models shown in this figure are also given in Table 1. The
table contains the effective ages of the globular cluster
candidates from both the DENSE BASIS and SSP fitting
methods, which generally agree within the uncertainties. Of
the objects under consideration, six (IDs 1, 2, 4, 8, 9, and 10)
are consistent with SFHs that peaked at early formation times.
Note that we do not include object 9 in our list of globular
cluster candidates because of its low signal-to-noise ratio
(S/N), coupled with possible contamination from the nearby
diffraction spike and extended tail visible in Figure 1. Objects
11 and 12, which are in the bulk of the galaxy, show recent star
formation, consistent with the [OIII] λ5007 emission in
Figure 3. While these could be younger star clusters that
might evolve into globular clusters, they happen to be
completely overlapping with the bulk of the galaxy, and
disentangling the light of the compact source from that of the
Table 1
Observed Photometric Properties and Derived Physical Parameters for the Compact Point Sources Estimated from DENSE BASIS and the SSP Fitter
ID 1 2 3 4 5 6 7 8 9 10 11 12
Classa
GC GC C GC E E B GC C GC B B
Fν [nJy; F435W] L L L L L L 13.98 33.51 L L 38.17 155.42
δFν [nJy; F435W] L L L L L L ±4.57 ±4.72 L L ±4.57 ±4.63
Fν [nJy; F606W] L L L L 20.28 20.98 21.20 L L L 102.37 231.08
δFν [nJy; F606W] L L L L ±3.24 ±3.28 ±3.16 L L L ±3.15 ±3.08
Fν [nJy; F814W] L L L L 52.41 L 46.52 L 67.55 L 126.44 258.67
δFν [nJy; F814W] L L L L ±4.49 L ±4.54 L ±4.58 L ±4.62 ±4.54
Fν [nJy; F090W] 2.40 3.00 19.05 L 25.70 17.66 72.54 17.40 6.40 7.45 178.21 249.38
δFν [nJy; F090W] ±2.27 ±2.26 ±2.34 L ±2.41 ±2.42 ±1.78 ±2.30 ±2.35 ±2.34 ±1.77 ±1.87
Fν [nJy; F150W] 20.12 17.11 22.25 35.21 48.47 34.82 69.74 77.23 19.80 52.99 285.08 334.33
δFν [nJy; F150W] ±5.32 ±5.33 ±5.28 ±5.28 ±5.28 ±5.28 ±5.35 ±5.29 ±5.25 ±5.29 ±5.35 ±5.32
Fν [nJy; F200W] 41.05 72.04 41.53 35.97 44.43 32.12 82.67 91.62 22.36 60.53 328.86 271.68
δFν [nJy; F200W] ±5.03 ±5.04 ±5.09 ±5.12 ±5.09 ±5.14 ±5.07 ±5.08 ±5.11 ±5.08 ±5.07 ±5.04
Fν [nJy; F277W] 51.28 67.68 73.76 75.72 60.01 33.99 60.36 104.96 21.52 82.81 455.34 351.27
δFν [nJy; F277W] ±7.21 ±7.19 ±7.24 ±7.23 ±7.24 ±7.34 ±7.10 ±7.25 ±7.33 ±7.23 ±7.04 ±7.06
Fν [nJy; F356W] 46.60 95.96 55.93 58.01 57.21 27.74 98.49 111.25 10.54 88.50 502.32 345.09
δFν [nJy; F356W] ±7.20 ±7.21 ±7.17 ±7.21 ±7.21 ±7.16 ±7.03 ±7.20 ±7.14 ±7.21 ±6.44 ±6.98
Fν [nJy; F444W] 25.70 61.42 62.45 68.21 53.26 26.67 43.28 75.12 12.08 74.95 452.73 311.93
δFν [nJy; F444W] ±6.23 ±6.16 ±6.21 ±6.22 ±6.62 ±6.13 ±6.09 ±6.21 ±6.17 ±6.22 ±6.10 ±6.07
log M*,50
b
[Me] 8.26 8.57 8.42 8.57 8.34 8.15 8.20 8.68 7.96 8.58 9.09 8.41
log M*,16
b
[Me] 8.15 8.48 8.32 8.48 8.24 8.01 7.72 8.60 7.82 8.49 9.01 8.33
log M*,84
b
[Me] 8.38 8.67 8.52 8.68 8.45 8.27 8.34 8.77 8.10 8.67 9.14 8.49
log sSFR*,50 [yr−1
] −12.05 −12.25 −12.05 −12.15 −11.55 −11.05 −8.95 −12.45 −11.75 −12.25 −9.25 −8.35
log sSFR*,16 [yr−1
] −13.25 −13.35 −13.25 −13.35 −13.15 −12.95 −9.75 −13.35 −13.15 −13.35 −9.35 −8.45
log sSFR*,84 [yr−1
] −10.85 −11.05 −10.85 −10.95 −10.05 −9.55 −8.05 −11.35 −10.35 −11.15 −9.05 −8.25
tpeak, 50 [Gyr] 4.10 4.01 0.68 3.87 0.32 0.87 0.27 4.06 4.01 4.10 0.05 0.00
tpeak, 16 [Gyr] 2.60 2.51 0.68 2.27 0.32 0.07 0.27 2.46 3.01 2.60 0.05 0.00
tpeak, 84 [Gyr] 4.51 4.51 1.98 4.37 2.02 2.67 0.52 4.51 4.51 4.51 3.60 0.00
AV,50 [mag] 0.30 0.48 0.28 1.28 0.15 0.16 0.18 0.23 0.22 0.34 0.27 0.03
AV,16 [mag] 0.08 0.16 0.07 0.78 0.04 0.04 0.03 0.06 0.06 0.10 0.20 0.01
AV,84 [mag] 0.68 0.91 0.62 1.82 0.39 0.47 0.49 0.49 0.55 0.71 0.35 0.05
log Z50/Ze −0.51 −0.33 −0.47 −0.11 −1.04 −1.02 −0.82 −0.72 −0.72 −0.36 0.21 0.11
log Z16/Ze −1.09 −0.88 −1.05 −0.67 −1.37 −1.37 −1.43 −1.13 −1.25 −0.89 0.14 0.09
log Z84/Ze −0.02 0.05 0.01 0.16 −0.45 −0.41 −0.54 −0.24 −0.12 0.03 0.24 0.15
log M*,SSP [Me] 8.66 8.87 8.41 8.98 8.49 8.23 8.45 9.06 8.34 8.97 8.60 8.32
ageSSP [Gyr] 4.37 3.16 1.26 4.50 0.56 0.71 0.39 4.47 4.47 4.50 0.04 0.03
log Z/Ze,SSP −0.50 −0.26 −0.55 0.00 −1.47 −1.50 −1.50 −1.00 −1.50 −0.50 0.00 0.00
AV,SSP [mag] 0.11 0.43 0.23 1.00 0.60 0.22 0.00 0.12 0.00 0.18 0.71 0.06
DB
2
c / SSP
2
c 1.01 1.03 1.27 1.00 1.05 0.95 0.72 0.92 0.94 0.93 0.51 2.02
Notes. Reported uncertainties represent the 16th–84th percentiles of the posterior distribution for each quantity.
a
Categories for the individual objects: GC: globular cluster candidates; C: possibly contaminated by galactic light (or by a nearby diffraction spike for id 9); E:
extended sources from visual inspection; B: in the bulk of the galaxy or actively star-forming, for e.g., the OIII regions in Figure 4.
b
The stellar masses account for stellar mass loss but are not corrected for magnification factors, which are ∼10–100 and can vary across the image.
(This table is available in its entirety in machine-readable form.)
5
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
6. host is extremely difficult. As a result, the star formation
measured from the photometry is likely a combination of light
from both sources, which makes it difficult to speculate on their
nature as younger star clusters. With a larger data set of similar
galaxies from JWST observations such as presented by Laporte
et al. (2022), it might be possible to observe the formation and
evolution of globular clusters as it happens, and at higher
redshifts than previously possible.
Panel (a) of Figure 3 shows emission-line maps at the
redshifted wavelength of [OIII] λ5007 for all three images of
the Sparkler. Individual columns show the direct, F115W
image (the broadband filter within which the redshifted [OIII]
λ5007 emission lies), and a NIRCam F090W, F150W, and
F200W color composite for each Sparkler image. There is clear
evidence of [OIII] λ5007 emission in all three images, which
we interpret as related to star formation activity in the Sparkler.
Note that the line emission is spatially with the two blue
regions in the color composite, consistent with this interpreta-
tion. Most importantly, there is no evidence of line emission at
the locations of those sparkles that we have previously
identified as globular cluster candidates (IDs 1, 2, 4, 8, and
10), and this adds confidence to our conclusion that these
objects consist of old stellar populations and are devoid of
ongoing star formation.
Much can be learned from inter-comparing the images
shown in panel (a) of Figure 3, and in particular, from
comparing the properties of sparkles we identified in image 2
with their counterparts in images 1 and 3. We leave such
analysis, as well as the construction of a full lens model of the
system, to future papers; for now, we simply highlight a few
tentatively matched features in the third column of this panel,
focusing on the globular cluster candidates (pink labels) and the
two most prominent star-forming regions (cyan labels).
We close this section with some preliminary discussion of
the mass of the Sparkler. Fits to the integrated photometry of
images 1 and 3 using DENSE BASIS recover log stellar masses
of 9.67 0.09
0.08
-
+
Me and 9.51 0.08
0.08
-
+
Me, respectively for the host
galaxy (uncorrected for magnification), and SFHs that show a
recent rise over the last ∼Gyr. We do not fit image 2 due to the
strong differential magnification. Assuming a magnification of
∼5 for image 1 (the average magnification from the Caminha
et al. (2022) and Mahler et al. (2022) models), the stellar mass
of Sparkler would be around 109
Me, which is similar to that of
the Large Magellanic Cloud (Erkal et al. 2019), which has ∼40
globular clusters (Bennet et al. 2022).
5. Discussion
We are at the earliest stages of understanding how best to
calibrate the in-flight data from JWST, so the SED modeling is
best approached with a degree of caution. For this reason, we
emphasize that our most important conclusions spring from
observations that are independent of detailed SED modeling.
First, many of the compact sources in and around the Sparkler
are unresolved (panel (b) of Figure 3) and several can be cross-
identified in multiple images (Figure 1 and panel (a) in
Figure 3), so they are clearly associated with the host galaxy,
placing them at z = 1.378. The colors of these systems are
consistent with the expected positions of quiescent sources at
z = 1.378 on a rest-frame urJ diagram (panel (c) of Figure 3).
Independent of any modeling, these facts suggest an identifica-
tion of the red sparkles with evolved globular clusters.
Figure 3. (a) The globular cluster candidates associated with the main galaxy. Shown are the F115W images (left column), [OIII] λ5007 emission-line maps derived
from the NIRISS grism data in the F115W band (middle column), and NIRCam color composite images (right column). Sparkle IDs are shown for image 2, with
tentative counterparts identified in images 1 and 3. The lower part of the [OIII] λ5007 map of image 2 suffers from significant contamination. [OIII] λ5007 emission is
a classic signature of ongoing star formation; here, it is present in the star-forming regions of the host galaxy, but its absence at the locations of the globular cluster
candidates supports the hypothesis that at the epoch of observation these are quiescent systems. (b) The globular cluster candidates are unresolved. Fits to the globular
cluster candidates with point sources on the 0 02 F150W images using GALFIT (Peng et al. 2010) show that the residuals are consistent with noise. (c) The globular
cluster candidates have colors of quenched stellar systems. The urJ colors (measured directly from F090W, F200W, and the average of the F277W and F356W fluxes)
compared with z ∼ 1.4 galaxies in the “Classic” COSMOS2020 catalog (Weaver et al. 2022). The integrated colors of the Sparkler galaxy (blue circle labeled as “Sp”)
are in the star-forming blue cloud, as are our other point sources (orange), but the globular cluster candidates (pink) have u
*
-r > 1.5 and are consistent with the colors
of quenched systems.
6
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
7. Going further than this requires modeling. At face value, the
reddest compact clumps (5 of the 12 in Table 1 and Figure 4)
surrounding the Sparkler show SFHs consistent with SSPs
formed at very high redshifts (z 9). Another two objects,
mainly in the bulk of the galaxy, show SFHs consistent with
younger (∼0.03–0.3 Gyr) stellar populations. A primary
determinant of these compact sources being globular clusters
rather than satellite dwarf galaxies are the sizes and stellar mass
surface densities. However, given the limits of JWST’s
resolution and the uncertainties in lens modeling, a full
analysis of these quantities is beyond the scope of this work.
Assuming that the sparkles are smaller than the FWHM of the
NIRCam/F150W PSF (FWHM ∼ 0 05) we calculate an upper
limit on the sizes of these objects to be ∼2–22 pc for the μ = 10
and μ = 100 cases respectively. This results in stellar mass
surface densities of Σ ∼ 0.7−7 × 104
Me/pc2
or higher,
consistent with being globular clusters (Carballo-Bello et al.
2012) rather than dwarf satellites (Herrmann et al. 2016).
The quiescent nature of the reddest point sources in and
around the Sparkler effectively rules out the possibility that
they are active star formation complexes of the kind seen in
many 1 < z < 3 galaxies, such as those associated with
dynamical instabilities in gas-rich turbulent disks (Förster
Schreiber et al. 2006; Genzel et al. 2006). A number of studies
examining clumps in high-redshift systems with strong
gravitational lensing have been able to explore the clump size
distribution at physical spatial resolutions below 100 pc (e.g.,
Livermore et al. 2012; Wuyts et al. 2014; Livermore et al.
2015; Johnson et al. 2017; Welch et al. 2022a). These report a
broad range of sizes (50 pc–1 kpc), but because of the high
magnification of the Sparkler, most such clumps would be
expected to be resolved by the JWST data we study. As already
noted, the pioneering work by Johnson et al. (2017) and
Vanzella et al. (2017) suggests that HST observations of
strongly lensed active star formation complexes in galaxies at
2 < z < 6 may already have captured the earliest phases of
globular cluster formation. More recent work on lensed z ∼ 6
galaxies has revealed even smaller complexes, e.g., in the
Sunrise Arc (Welch et al. 2022b). This work is exciting, but the
association of young massive clusters at high redshift with
proto-globular clusters remains indirect, and the future
evolution of these star formation complexes is unclear.
The most interesting interpretation of the clumps in and
around the Sparkler is that the bulk of them are evolved
Figure 4. Nonparametric SFHs derived from fitting the photometric SEDs of the individual sparkles. Pink points and curves show the locations and colors (top left),
SFHs (marked panels), and SED fits (inset panels) of the individual globular cluster candidates, while orange is used to show the fits and SFHs for objects that are
extended sources, heavily contaminated by light from the galaxy, nearby objects or ICL, or in the body of the main galaxy. Even though object 9 is consistent with an
early SFH, we exclude it as a globular cluster candidate due to its low S/N and possible contamination by a nearby diffraction spike. The SEDs are shown in Fν units,
with the spectra corresponding to the best-fit model from DENSE BASIS. The SFR values are not corrected for lensing magnification, which could make them ∼10–100
times smaller. zpeak corresponds to the redshift at which the posterior SFH peaks in SFR. Overall, the globular cluster candidates show SFHs consistent with very early
epochs of star formation ranging over 7 < z < 11.
7
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
8. (maximally old, given the 4.6 Gyr age of universe at the epoch
of observation) globular clusters. This is also consistent with
Sameie et al. (2022), who find that globular cluster formation in
lower-mass galaxies occurs at redshifts of ∼5–10. If this
interpretation is correct, JWST observations of quiescent,
evolved globular clusters around z ∼ 1.5 galaxies can be used
to explore the formation history of globular clusters in a
manner that is complementary to searching directly for the
earliest stages of globular cluster formation (e.g., by examining
young massive star formation complexes at z ∼ 6 and higher;
Boylan-Kolchin 2017, 2018). Young star formation complexes
may, or may not, evolve eventually into globular clusters, but
there can be little doubt about the identity of an isolated and
quiescent compact system if its mass is around 106
Me and its
scale length is a few parsecs. JWST observations of evolved
globular clusters at z ∼ 1.5 are also complementary to
exploring the ages of local globular clusters, as models fit to
local globular clusters cannot distinguish between old and very
old systems. For example, distinguishing between an
∼11.5 Gyr old stellar population that formed at z = 3 and a
13.2 Gyr old stellar population that formed at z = 9 is not
possible with current models and data, because they are
degenerate with respect to a number of physical parameters
(Ocvirk et al. 2006; Conroy et al. 2009, 2010). JWST
observations of evolved globular clusters, seen when the
universe was about one third of its present age, provide an
opportunity for progress by “meeting in the middle”, because
population synthesis models of integrated starlight from SSPs
can distinguish rather easily between the ages of young-
intermediate stellar populations. This is because intermediate-
mass stars with very distinctive photospheric properties are
present at these ages. At z = 1.378, the lookback time to the
Sparkler is 9.1 Gyr, and the age of the universe at that epoch is
4.6 Gyr. Distinguishing between z = 3 and z = 9 formation
epochs for the globular cluster system corresponds to
distinguishing between 2.4 Gyr and 4.1 Gyr old populations,
which is relatively straightforward for population synthesis
models in the JWST bands. In the case of the Sparkler, the
striking conclusion is that at least foir of its globular clusters
have likely formed at z > 9.
Our identification of the sparkles in Figure 1 with evolved
globular clusters relies on an assumption of very strong
magnification of the Sparkler. Strong magnification occurs only
in narrow regions near lensing caustics, so there are strong
magnification gradients in the source plane. This makes it
difficult to invert lens models to compute accurate luminosity
functions for the putative globular cluster population. Based on
Figure 1, we assume the overall magnification of the system is
large (at least a factor of 15), but handling the strong
magnification gradients across the local environment of the
Sparkler is beyond the scope of this paper. Assuming
magnifications of 10–100, the stellar masses of these point
sources fall in the range ∼ 106
−107
Me, which is plausible for
metal-poor globular clusters seen at ages of around 4 Gyr,
although most lie at the high end of the local globular cluster
mass range. Since a critical curve may be running through the
system, we emphasize again that the magnification (and hence
the masses) of the clusters is very uncertain.
If lens models can be determined with the accuracy needed
to compute the source plane luminosity functions and mass
distributions, then the Sparkler may place interesting con-
straints on globular cluster dissolution. Physical processes
slowly dissolve globular clusters, and luminosity evolution is
significant, so distant globular clusters are expected to be both
more massive and more luminous than their local counterparts
(Webb & Leigh 2015; Goudfrooij 2018). The most relevant
physical processes are stellar evolution coupled with relaxation
and tidal effects, and in some models significant mass loss is
expected. For example, with a standard Kroupa initial mass
function (IMF) (Kroupa 2001) about 30% of the mass of a star
cluster is expected to be lost due to stellar evolution alone in the
first few Gyr (Baumgardt & Makino 2003), and this fraction is
much higher for top-heavy IMFs. Dynamical processes would
compound this loss, though dynamical processes are likely to be
most significant for lower-mass clusters (Baumgardt 2006). In
any case, unless globular cluster dissolution processes are
operating far more quickly than expected, very high magnifica-
tions are certainly needed to explain the point sources
surrounding the Sparkler as globular clusters.
6. Conclusions
In situ investigations of evolved globular cluster systems at
z ∼ 1.5 present us with a golden opportunity to probe the initial
formation epoch of globular clusters with a precision
unobtainable from studying local systems. Magnified red point
sources seen at this epoch are old enough to be unambiguously
identified as globular clusters, but young enough that their ages
can be determined quite reliably. We applied this idea to JWST
and HST observations of a z = 1.378 galaxy (which we refer to
as the Sparkler), which is strongly lensed by the z = 0.39
galaxy cluster SMACS0723. At least 5 of the 12 compact
sources in and around the Sparkler are unresolved and red, and
the most likely interpretation of these is that they are evolved
globular clusters seen at z = 1.378. By modeling the colors and
spectra of these compact sources with the DENSE BASIS
method, four (33%) are found to be consistent with a SSP
forming at z > 9, i.e., in the first 0.5 Gyr of cosmic history and
more than 13 Gyr before the present epoch. If these ages are
confirmed, at least some globular clusters appear to have
formed contemporaneously with the large-scale reionization of
the intergalactic medium, hinting at a deep connection between
globular cluster formation and the initial phases of galaxy
assembly. Data and code to reproduce our results will be made
available at http://canucs-jwst.com/sparkler.html.
We thank the anonymous referee for their thorough reading
and constructive comments that helped make this work more
rigorous. The authors thank Duncan Forbes and Mike Boylan-
Kolchin for their helpful comments on the manuscript. This
work is based in part on observations made with the NASA/
ESA/CSA James Webb Space Telescope. The data were
obtained from the Mikulski Archive for Space Telescopes
(https://doi.org/10.17909/se6w-0h98) at the Space Telescope
Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA
contract NAS 5-03127 for JWST. The Early Release Observa-
tions and associated materials were developed, executed, and
compiled by the ERO production team: Hannah Braun, Claire
Blome, Matthew Brown, Margaret Carruthers, Dan Coe,
Joseph DePasquale, Nestor Espinoza, Macarena Garcia Marin,
Karl Gordon, Alaina Henry, Leah Hustak, Andi James, Ann
Jenkins, Anton Koekemoer, Stephanie LaMassa, David Law,
Alexandra Lockwood, Amaya Moro-Martin, Susan Mullally,
Alyssa Pagan, Dani Player, Klaus Pontoppidan, Charles
8
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.
9. Proffitt, Christine Pulliam, Leah Ramsay, Swara Ravindranath,
Neill Reid, Massimo Robberto, Elena Sabbi, Leonardo Ubeda.
The EROs were also made possible by the foundational efforts
and support from the JWST instruments, STScI planning and
scheduling, and Data Management teams.
This research was supported by Natural Sciences and
Engineering Research Council (NSERC) of Canada Discovery
Grants to RA, AM, and MS, by an NSERC Discovery
Accelerator to MS, and by a grant from the Canadian Space
Agency to the NIRISS GTO Team (18JWST-GTO1). M.B.
acknowledges support from the Slovenian national research
agency ARRS through grant N1-0238. Funding from the
Dunlap Institute for Astronomy & Astrophysics is gratefully
acknowledged. The Dunlap Institute is funded through an
endowment established by the David Dunlap family and the
University of Toronto. This research used the Canadian
Advanced Network For Astronomy Research (CANFAR)
operated in partnership by the Canadian Astronomy Data
Centre and The Digital Research Alliance of Canada with
support from the National Research Council of Canada, the
Canadian Space Agency, CANARIE and the Canadian
Foundation for Innovation. C.P. is supported by the Canadian
Space Agency under a contract with NRC Herzberg Astronomy
and Astrophysics.
Facilities: JWST, HST(ACS).
Software: astropy (Astropy Collaboration et al. 2013,
2018), Photutils (Bradley et al. 2021), Cloudy (Ferland et al.
2013), SEP (Barbary 2016; Bertin & Arnouts 1996), SEx-
tractor (Bertin & Arnouts 1996), FSPS (Johnson et al.
2021), Dense Basis (Iyer et al. 2021), matplotlib (Caswell
et al. 2019), scipy (Virtanen et al. 2020), numpy (Walt et al.
2011), corner (Foreman-Mackey 2016), hickle (Price
et al. 2018), GALFIT (Peng et al. 2010).
ORCID iDs
Lamiya Mowla https:/
/orcid.org/0000-0002-8530-9765
Kartheik G. Iyer https:/
/orcid.org/0000-0001-9298-3523
Guillaume Desprez https:/
/orcid.org/0000-0001-8325-1742
Vicente Estrada-Carpenter https:/
/orcid.org/0000-0001-
8489-2349
Nicholas S. Martis https:/
/orcid.org/0000-0003-3243-9969
Ghassan T. Sarrouh https:/
/orcid.org/0000-0001-8830-2166
Victoria Strait https:/
/orcid.org/0000-0002-6338-7295
Yoshihisa Asada https:/
/orcid.org/0000-0003-3983-5438
Gabriel Brammer https:/
/orcid.org/0000-0003-2680-005X
Marcin Sawicki https:/
/orcid.org/0000-0002-7712-7857
Chris J. Willott https:/
/orcid.org/0000-0002-4201-7367
Marusa Bradac https:/
/orcid.org/0000-0001-5984-0395
René Doyon https:/
/orcid.org/0000-0001-5485-4675
Adam Muzzin https:/
/orcid.org/0000-0002-9330-9108
Camilla Pacifici https:/
/orcid.org/0000-0003-4196-0617
Swara Ravindranath https:/
/orcid.org/0000-0002-
5269-6527
Johannes Zabl https:/
/orcid.org/0000-0002-9842-6354
References
Astropy Collaboration, Price-Whelan, A. M., Sipőcz, B. M., et al. 2018, AJ,
156, 123
Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A,
558, A33
Barbary, K. 2016, JOSS, 1, 58
Baumgardt, H. 2006, arXiv:0605125
Baumgardt, H., & Makino, J. 2003, MNRAS, 340, 227
Bennet, P., Alfaro-Cuello, M., del Pino, A., et al. 2022, ApJ, 935, 149
Bertin, E., & Arnouts, S. 1996, A&AS, 117, 393
Boylan-Kolchin, M. 2017, MNRAS, 472, 3120
Boylan-Kolchin, M. 2018, MNRAS, 479, 332
Bradley, L., Sipőcz, B., Robitaille, T., et al. 2021, astropy/photutils: 1.1.0,
1.1.0, Zenodo, Zenodo, doi:10.5281/zenodo.4624996
Brammer, G., & Matharu, J. 2021, gbrammer/grizli: Release 2021, 1.3.2,
Zenodo, Zenodo, doi:10.5281/zenodo.5012699
Brammer, G. B., van Dokkum, P. G., & Coppi, P. 2008, ApJ, 686, 1503
Brodie, J. P., & Strader, J. 2006, ARA&A, 44, 193
Caminha, G. B., Suyu, S. H., Mercurio, A., et al. 2022, arXiv:2207.07567
Carballo-Bello, J. A., Gieles, M., Sollima, A., et al. 2012, MNRAS,
419, 14
Carlberg, R. G. 2002, ApJ, 573, 60
Caswell, T., Droettboom, M., Hunter, J., et al. 2019, matplotlib/matplotlib v3.
1.0, Zenodo, doi:10.5281/zenodo.2893252
Coe, D., Salmon, B., Bradač, M., et al. 2019, ApJ, 884, 85
Conroy, C., Gunn, J. E., & White, M. 2009, ApJ, 699, 486
Conroy, C., White, M., & Gunn, J. E. 2010, ApJ, 708, 58
de Grijs, R., O’Connell, R. W., & Gallagher, J. S. I. 2001, AJ, 121, 768
Doyon, R., Hutchings, J. B., Beaulieu, M., et al. 2012, Proc. SPIE, 8442,
84422R
Erkal, D., Belokurov, V., Laporte, C. F. P., et al. 2019, MNRAS, 487,
2685
Ferland, G. J., Porter, R. L., van Hoof, P. A. M., et al. 2013, RMxAA,
49, 137
Forbes, D. A., Bastian, N., Gieles, M., et al. 2018, RSPSA, 474, 20170616
Foreman-Mackey, D. 2016, JOSS, 1, 24
Förster Schreiber, N. M., Genzel, R., Lehnert, M. D., et al. 2006, ApJ,
645, 1062
Freeman, K. C., & Norris, J. 1981, ARA&A, 19, 319
Genzel, R., Tacconi, L. J., Eisenhauer, F., et al. 2006, Natur, 442, 786
Golubchik, M., Furtak, L. J., Meena, A. K., & Zitrin, A. 2022, arXiv:2207.
05007
Goudfrooij, P. 2018, ApJ, 857, 16
Harris, W. E., & Racine, R. 1979, ARA&A, 17, 241
Herrmann, K. A., Hunter, D. A., & Elmegreen, B. G. 2016, AJ, 151, 145
Iyer, K., & Gawiser, E. 2017, ApJ, 838, 127
Iyer, K., Gawiser, E., Davé, R., et al. 2018, ApJ, 866, 120
Iyer, K. G., Gawiser, E., Faber, S. M., et al. 2019, ApJ, 879, 116
Iyer, K. G., Gawiser, E., Faber, S. M., et al. 2021, dense_basis: Dense Basis
SED fitting, Astrophysics Source Code Library, record ascl:2104.015
Johnson, B., Foreman-Mackey, D., Sick, J., et al. 2021, dfm/python-fsps:
python-fsps v0.4.1rc1, Zenodo, doi:10.5281/zenodo.4737461
Johnson, C. I., Caldwell, N., Rich, R. M., et al. 2017, ApJ, 836, 168
Kroupa, P. 2001, MNRAS, 322, 231
Laporte, N., Zitrin, A., Dole, H., et al. 2022, arXiv:2208.04930
Leja, J., Carnall, A. C., Johnson, B. D., Conroy, C., & Speagle, J. S. 2019, ApJ,
876, 3
Livermore, R. C., Jones, T., Richard, J., et al. 2012, MNRAS, 427, 688
Livermore, R. C., Jones, T. A., Richard, J., et al. 2015, MNRAS, 450, 1812
Lower, S., Narayanan, D., Leja, J., et al. 2020, ApJ, 904, 33
Mahler, G., Jauzac, M., Richard, J., et al. 2022, arXiv:2207.07101
Ocvirk, P., Pichon, C., Lançon, A., & Thiébaut, E. 2006, MNRAS, 365, 46
Olsen, C., Gawiser, E., Iyer, K., et al. 2021, ApJ, 913, 45
Peebles, P. J. E., & Dicke, R. H. 1968, ApJ, 154, 891
Peng, C. Y., Ho, L. C., Impey, C. D., & Rix, H.-W. 2010, AJ, 139, 2097
Pontoppidan, K., Blome, C., Braun, H., et al. 2022, ApJL, 936, L14
Price, D. C., van der Velden, E., Celles, S., et al. 2018, JOSS, 3, 1115
Renzini, A. 2017, MNRAS, 469, L63
Rieke, M. J., Kelly, D., & Horner, S. 2005, Proc. SPIE, 5904, 1
Sameie, O., Boylan-Kolchin, M., Hopkins, P. F., et al. 2022, arXiv:2204.00638
Schweizer, F., & Seitzer, P. 1998, AJ, 116, 2206
Trujillo-Gomez, S., Kruijssen, J. M. D., Reina-Campos, M., et al. 2021,
MNRAS, 503, 31
Vanzella, E., Calura, F., Meneghetti, M., et al. 2017, MNRAS, 467, 4304
Vanzella, E., Castellano, M., Bergamini, P., et al. 2022, arXiv:2208.00520
Virtanen, P., Gommers, R., Oliphant, T. E., et al. 2020, NatMe, 17, 261
Walt, S. v. d., Colbert, S. C., & Varoquaux, G. 2011, CSE, 13, 22
Weaver, J. R., Kauffmann, O. B., Ilbert, O., et al. 2022, ApJS, 258, 11
Webb, J. J., & Leigh, N. W. C. 2015, MNRAS, 453, 3278
Welch, B., Coe, D., Zitrin, A., et al. 2022a, arXiv:2207.03532
Welch, B., Coe, D., Diego, J. M., et al. 2022b, Natur, 603, 815
Willott, C. J., Doyon, R., Albert, L., et al. 2022, PASP, 134, 025002
Wuyts, E., Rigby, J. R., Gladders, M. D., & Sharon, K. 2014, ApJ, 781, 61
9
The Astrophysical Journal Letters, 937:L35 (9pp), 2022 October 1 Mowla et al.