It's the talk I gave in the Pucon Symposium 2015 about the Next Generation Fornax Survey and the discovery of a large number of dwarf galaxies in the Fornax cluster.

1. Pucón Symposium 2015
Puerto Varas, Agosto 2015
Chasing ghost galaxies in the Fornax cluster
Opportunities for the Deep Learning
community
Paul Eigenthaler, Thomas Puzia, Matt Taylor,
Yasna Ordenes, Simón Angel, Maren Hempel
Ariane Lançon, Steffen Mieske, Michael Hilker,
Patrick Côté, Laura Ferrarese & NGFS team.
Roberto Muñoz
Instituto de Astrofísica
Pontificia Universidad Católica de Chile

2. Galaxy clusters
Gravitationally bound structures that contain from hundreds to
thousands of galaxies. They are dominated by dark matter (85%) and
have large amounts of hot gas (10%).
Why so interesting?
• Large amount of galaxies at the same distance
• Laboratories to study the influence of
environment
• Rare objects formed from the most overdense
peaks in the initial density field
Coma is the best studied cluster
• Distance of 100 Mpc
• More than 1,000 members
• Mass of about
Roberto Muñoz
2 ⇥ 1015
M

3. Diffuse galaxies in Coma
van Dokkum et al. (2015) published a paper with 47 new dwarf
galaxies. A couple are diffuse galaxies, sizes similar to the Milky Way
but much fainter.
Roberto Muñoz

4. Virgo and Fornax clusters
Virgo is the largest nearby galaxy cluster. It contains about 1,762
members (Binggeli et al. 1985) and is located at 16.5 Mpc
Fornax is the second closest cluster. It contains about 340 members
(Ferguson et al. 1989) and is located at 20.0 Mpc.
Roberto Muñoz
Virgo cluster in X-ray from ROSAT
(Böhringer et al. 1994)
Murakami et al. [Vol. ,
–4.0 keV) image of the Fornax cluster. The NXB was subtracted and the difference in exposure
Fornax cluster in X-ray from XMM.
(Murakami et al 2011)

5. Virgo and Fornax clusters
Virgo is the largest nearby galaxy cluster. It contains about 1,762
members (Binggeli et al. 1985) and is located at 16.5 Mpc
Fornax is the second closest cluster. It contains about 340 members
(Ferguson et al. 1989) and is located at 20.0 Mpc.
Roberto Muñoz
Virgo cluster in X-ray from ROSAT
(Böhringer et al. 1994)
Murakami et al. [Vol. ,
–4.0 keV) image of the Fornax cluster. The NXB was subtracted and the difference in exposure
Fornax cluster in X-ray from XMM.
(Murakami et al 2011)
Ferrarese et al. 2012

6. The uiK diagram
Roberto Muñoz
Muñoz et al. 2014
Ferrarese et al. 2012
Globular
clusters

7. The improved uiK diagram
Roberto Muñoz
Powalka et al., in preparation

8. NGFS: Fornax cluster
The Next Generation Fornax Survey (NGFS; PI: R. Muñoz) is an
ongoing multipassband optical and NIR survey of the Fornax galaxy
cluster. It will cover the central 30 deg2 out to the virial radius and will
allow to study the GC and galaxy populations.
Roberto Muñoz
8 deg
Globular
clusters
Galaxies

9. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

10. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

11. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

12. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

13. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

14. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

15. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

16. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

17. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

18. Observations and Processing
There is no universal observational strategy neither universal image
processing pipeline. It all depends on the scientific goals of the project
and the instrument been used.
Roberto Muñoz
CTIO/DECam
1
2
3
4
5
6
7
10
13

19. Observations and Processing
Roberto Muñoz
Raw
CP detrended NGFS pipeline

20. Registration and stacking
Roberto Muñoz

21. Registration and stacking
Roberto Muñoz
Exposure=300s

22. Registration and stacking
Roberto Muñoz
Exposure=300s Exposure=17x300s
= 1.5 hours

23. Registration and stacking
Roberto Muñoz
Exposure=300s Exposure=17x300s
= 1.5 hours
Dwarf galaxies

24. Color image asinh
The survey is still ongoing, but we already have deep u, g and i-band
for several tiles.
Roberto Muñoz
Muñoz et al., 2015

25. Color image asinh
The survey is still ongoing, but we already have deep u, g and i-band
for several tiles.
Roberto Muñoz
Muñoz et al., 2015

26. Color image asinh
The survey is still ongoing, but we already have deep u, g and i-band
for several tiles.
Roberto Muñoz
Muñoz et al., 2015

27. Dwarfs galaxies
We have discovered 200 new dwarf galaxies just in the central 3 deg2
of the Fornax cluster. Still 27 deg2 more to explore.
Roberto Muñoz
Muñoz, Eigenthaler, Puzia,Taylor et al., 2015

28. Equivalent to IGM
between Milky Way
and Andromeda
(~780 kpc)
Milky Way
Andromeda
•~70 deg2
•u’g’r’i’z’
•~3σ past GCLF
turnover
•~26-27 mag/arcsec^2
•spatial extent of
Centaurus A’s ~300
kpc virial radius
*optical
SCABS: A Survey of Centaurus
A’s Baryonic Structures
SCABS: A Survey of Centaurus
A’s Baryonic Structures
Taylor et al.,
in preparation

29. Summary
The NGFS survey is a multi wavelength optical and NIR survey
of the Fornax cluster.
We have developed new algorithms and methods for doing
image processing of DECam data. Special focus on modelling
the spatial variations of the sky.
We have done visual classification of the central tile and it’s
exhausting. We have discovered 200 new dwarf galaxies just in
the central DECam tile.
We need to invite the community to help us with the
identification. There are opportunities for the researchers
working in deep learning to develop methods to automatise the
identification of dwarf galaxies.
Roberto Muñoz