This document discusses the asymmetry and star formation rate of dwarf spiral galaxies. It analyzes the asymmetry parameter (A) and star formation rate (SFR) values of 9 dwarf spiral galaxies using CAS morphological parameters and H-alpha emission fluxes. A positive correlation was found between A and SFR, with SFR increasing linearly with A. The conclusions note some galaxies had unusual Sersic indices possibly related to bars, and that A and SFR were generally correlated for these dwarf spiral galaxies.

1. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
The asymmetry and star formation rate for dwarf
spiral galaxies
M.Sc. Ignacio Vega Acevedo
Dr. Ana Mar´ıa Hidalgo G´amez
Departamento de F´ısica, ESFM-IPN
August 10, 2013
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

2. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
1 Introduction
CAS system
2 Sample of galaxies
3 Data Analysis
4 Asymmetry
5 Star formation rate
6 Relationship between A and SFR
7 Conclusions
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

3. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Introduction
dS galaxy
The dwarf spiral galaxies,dS are the galaxies with an optical
radius 5 Kpc, a magnitude MB − 18 (Hidalgo-G´amez, 2004).
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

4. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
CAS system
The CAS system is defined by the morphological parameters
Concentration, C, asymmetry, A and clumpiness, S (Conselice et
al., 2000).
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

5. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
C definition
Concentration measured how concentrate is the galaxy’s light
distribution
C ≡ 5 × log
r80
r20
∝
MS,G (T)
MS (T)
, 2 C 5,
where r80 and r20 are the radius with 80% and 20% of the total
galaxy luminosity (Kent, 1985). Conselice (2003) said that C is
proportional to gravitational gas mass, into stars, MS,G (T),
divided by the stellar mass, MS (T) where T is the actual age of
the galaxy.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

6. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
S definition
The clumpiness measures the spacial distribution for irregularities.
S =
I − B
I
∝
T
0
t
T
α (t) MG (t)
Ms (T)
dt,
where I is the original image and B is the image in the narrow
filter. Conselice (2003) said that S is proportional to α, which is
the SFR and the gas mass of system, MG . In this case T is the
actual age of the galaxy.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

7. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
A definition
The asymmetry parameter, A, measure the symmetry of the
galaxy’s image. The expression of asymmetry is:
A ≡
Σ |I − R|
2Σ (I)
∝
T
0
t
T
| ˙Ms (t)|
Ms (T) dt,
where I is the original image and R is the image rotated θ
(Abraham et al. 1996). The ˙Ms(t) is the temporal variation of
stellar mass, t and T have the same meaning that in S (Conselice,
2003).
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

8. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
Example of asymmetry
UGC 6205
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

9. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
CAS system
If ˙Ms(t) , MG (t) and α (t) are constant, the parameters A and S
will have the expression
A ∝
T ˙Ms
2Ms (T)
, S ∝
TαMG
2Ms (T)
,
then
S ∝

αMG
˙Ms

 A.
The constant of proportionality between S y A depending on SFR.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

10. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Our sample of galaxies dS
This sample of galaxies follows the definition of dwarf spiral galaxy
given by Hidalgo-G´amez (2004).
Galaxy
i
[degree]
r25
[kpc]
D
[Mpc]
MB
Av
[mag]
UGC891 63 3.13 9.4 ± 1 -15.32 0.076
UGC3775 27 4.68 20.8 ± 7.7 -15.08 0.305
UGC5242 50 4.86 24.76 ± ... -16.60 0.417
UGC5296 29 3.02 20.28 ± ... -15.08 0.031
UGC6205 41 4.99 18.87 ± ... -16.53 0.043
UGC6304 39 4.72 23.51 ± ... -15.40 0.029
UGC9570 14 ... 29.4 ± ... -15.89 0.029
UGC11820 24 4.96 17.1 ± 2.4 -14.70 0.332
UGC12212 56 3.3 14.7 ± 2.8 -15.11 0.170
Taken from: RC3; Hidalgo-G´amez, 2004; Fitzpatrick, 1999
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

11. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
These galaxies were observed in the filters R, V, Hα and
continuum. The observations were done with the telescope of
1.5m in Observatorio Astron´omico Nacional in San Pedro M´artir
by Dr. Ana Mar´ıa Hidalgo G´amez.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

12. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Data Analysis
The brightness profile expression:
I (r) = I0e
− r
r0
1
n
,
In order to increase the
signal-to-noise ratio, the profile was
taken in preferential directions.
UGC6205
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

13. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Galaxy
V filter R filter
n r0 [arcsec] rP [arcsec] n r0 [arcsec] rP [arcsec]
UGC 891 0.6 ± 0.4 13.0 ± 2.2 27.3 ± 4.6 0.7 ± 0.3 14.4 ± 2.3 30.2 ± 4.8
UGC 3775 0.5 ± 0.3 10.7 ± 2.5 22.5 ± 5.3 0.6 ± 0.3 11.0 ± 2.0 23.1 ± 4.2
UGC 11820 0.7 ± 0.3 10.6 ± 1.4 22.3 ± 2.9 0.9 ± 0.2 11.6 ± 1.4 24.4 ± 2.9
UGC 5296 2.0 ± 0.2 19.5 ± 2.5 41.0 ± 5.3 1.9 ± 0.2 22.3 ± 2.5 46.8 ± 5.3
UGC 6205 1.6 ± 0.3 20.9 ± 2.3 43.9 ± 4.8 1.7 ± 0.2 22.5 ± 2.6 47.3 ± 5.5
UGC 6304 1.5 ± 0.7 27.1 ± 2.4 56.9 ± 5.0 1.4 ± 0.6 1.4 ± 1.1 2.9 ± 2.3
UGC 9570 1.7 ± 0.2 26.0 ± 2.2 54.6 ± 4.6 1.7 ± 0.4 28.5 ± 2.2 59.9 ± 4.6
UGC 12212 1.5 ± 0.2 15.4 ± 2.1 32.3 ± 4.4 1.3 ± 0.1 16.3 ± 2.3 34.2 ± 4.8
UGC 5242 2.1 ± 0.4 14.8 ± 2.1 31.1 ± 4.4 2.1 ± 0.8 15.8 ± 1.9 33.2 ± 4.0
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

14. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Asymmetry for rP
Galaxy Filter θ = 450 θ = 900 θ = 1800
UGC 891
V 0.14 ± 0.02 0.18 ± 0.02 0.18 ± 0.02
R 0.13 ± 0.01 0.15 ± 0.01 0.17 ± 0.01
UGC 3775
V 0.20 ± 0.01 0.28 ± 0.01 0.32 ± 0.01
R 0.23 ± 0.01 0.29 ± 0.01 0.32 ± 0.01
UGC 5242
V 0.09 ± 0.01 0.13 ± 0.01 0.16 ± 0.01
R 0.11 ± 0.04 0.14 ± 0.03 0.17 ± 0.03
UGC 5296
V 0.12 ± 0.01 0.11 ± 0.01 0.09 ± 0.02
R 0.16 ± 0.04 0.14 ± 0.05 0.09 ± 0.07
UGC 6205
V 0.07 ± 0.02 0.09 ± 0.01 0.07 ± 0.02
R 0.07 ± 0.01 0.08 ± 0.01 0.07 ± 0.01
UGC 6304
V 0.09 ± 0.01 0.11 ± 0.01 0.12 ± 0.01
R 0.09 ± 0.01 0.12 ± 0.01 0.12 ± 0.01
UGC 9570
V 0.07 ± 0.01 0.10 ± 0.01 0.09 ± 0.01
R 0.07 ± 0.04 0.08 ± 0.04 0.08 ± 0.04
UGC 11820
V 0.13 ± 0.02 0.15 ± 0.01 0.15 ± 0.01
R 0.01 ± 0.04 0.02 ± 0.03 0.02 ± 0.03
UGC 12212
V 0.12 ± 0.02 0.18 ± 0.01 0.22 ± 0.01
R 0.09 ± 0.04 0.14 ± 0.03 0.17 ± 0.02
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

15. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Star formation rate
In this work the Hα emission was used for determined the SFR
using the expression,
SFR = 7.9 × 10−42
4πd2
FHα ,
where d is object’s distance and FHα is the flux (Kennicutt, 1983).
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

16. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Galaxy
Flux SFR
[erg*cm−2]*10−13 [M yr−1]*10−2
UGC 891 21.9 ± 0.4 1.9 ± 0.3
UGC 3775 14.7 ± 0.2 6.0 ± 0.3
UGC 5242 5.9 ± 0.1 3.4 ± 0.2
UGC 5296 6.3 ± 0.3 2.6 ± 0.3
UGC 6205 9.3 ± 0.1 3.2 ± 0.3
UGC 6304 10.8 ± 0.4 6.0 ± 0.2
UGC 9570 2.6 ± 0.1 2.1 ± 0.2
UGC 11820 2.5 ± 0.5 6.8 ± 0.3
UGC 12212 34.0 ± 0.1 5.2 ± 0.4
These values of SFR are of the same order as those obtained for
dwarf irregular galaxies (Zhang et al. 2011) and similar for
late-type (Hunter et al. 1998).
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

17. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
0,0 0,1 0,2 0,3 0,4 0,5
1
2
3
4
5
6
7
UGC 9570
UGC 891
UGC 6304
UGC 6205
UGC 5296
UGC 5242
UGC 3775
UGC 12212
SFR(Mo*yr^-1)x10^-2
A
UGC 11820
SFR = 7.8 (±2.2) A (V ) + 2.1 (±0.7) r = 0.63
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

18. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Conclusions
S´ersic index of these galaxies in some cases are very similar to
the disks of spiral galaxies, in others, the dwarf elliptical
galaxies. However three of them have very strange S´ersic
indices, possibly related to the existence of a bar.
It was found that the parameter A does not depend, in
general, the filter if they are contiguous.
We found that the SFR for these galaxies on average are of
the same order as irregular galaxies, 4M yr −1*10−2. This
means that the SFR of dS is more similar to the irregular
galaxies of normal spirals.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

19. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
On the whole sample of galaxies seem to follow a linear
correspondence, which is given mainly by the galaxies UGC
12212, UGC 6205, UGC 5242 and UGC3775.
With these results we can say that dS galaxies intena have a
structure more complex than previously thought.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

20. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Thanks for your attention.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

21. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
UGC6304, Hα - Hcon
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

22. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
SFR vs A in R
1
2
3
4
5
6
7
89
1
2
3
4
5
6
7
89
1
2
3
4
5
6
7
89
0,0 0,2 0,4 0,6
2
4
6
8
SFR(Mo*yr^-1)*10^-2
45
0,0 0,2 0,4 0,6
2
4
6
8
90
0,0 0,2 0,4 0,6
2
4
6
8
A
180
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

23. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Fitter of plot in R
SFR = (15.07 ± 5.79) A450 + 1.72 ± 1.15; r = 0.605
SFR = (11.06 ± 3.84) A900 + 1.72 ± 1.05; r = 0.638
SFR = (8.73 ± 2.61) A1800 + 2.14 ± 0.81; r = 0.702
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

24. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Inclination
r = r fe cos2 (φ) +
sin2
(φ)
cos2 (i)
(1)
Where r is the distance of barycentre in pixels, fe = 0.24arcsec
pixel is
plate scale, i is the inclination and φ is position angle.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

25. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Exposition time
Galaxy
Filter
V R Hα Hcon
UGC 891 1000 1200 3000 2400
UGC 3775 1200 1200 2300 1800
UGC 5242 1200 1000 3000 2400
UGC 5296 1400 1200 3300 2100
UGC 6205 1600 1200 3300 2700
UGC 6304 1200 1200 2300 1800
UGC 9570 1200 1200 3800 2100
UGC 11820 1200 900 3600 2400
UGC 12212 1000 1200 3600 2700
Exposition’s time giving in seconds.
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS

26. Introduction Sample of galaxies Data Analysis Asymmetry Star formation rate Relationship between A and SFR Conclusions
Barycentre [pixel]
Galaxy(1) Filter(2) Bx(3) By(4) Separation(5) [arcsec]
UGC891
V 414 357
0.96
R 417 360
UGC3775
V 249 647
0.96
R 245 644
UGC5242
V 501 463
1.68
R 505 458
UGC5296
V 432 53
0.72
R 433 529
UGC6205
V 479 381
0.72
R 479 378
UGC6304
V 601 376
0.72
R 601 366
UGC9570
V 737 754
0.48
R 739 755
UGC11820
V 668 451
0.96
R 665 465
UGC12212
V 540 473
1.2
R 540 479
I. Vega, A.M. Hidalgo Departamento de F´ısica, ESFM-IPN
Asymmetry and SFR for dS