Authors: Sarah Parker, Alyssa Likeness

Faculty Mentor: Adriana Durbala

Abstract:We explore the properties of lenticular galaxies in different environments (isolated galaxies versus crowded environments, i.e., groups with 4-10 galaxy members). Using aFortran code (BUDDA – Bulge Disk Decomposition Analysis), we model the photometric parameters that describe each lenticular galaxy in terms of size and light profile. Wethen compare the derived model-dependent measures between the two samples of galaxies to test if they are statistically different, which would hint at gravitationalinfluences of the neighbors. This process would allow us to gain more insight into the formation and evolution of lenticular galaxies.

Sample: N=12 CIG (isolated) & N=28 LGG (group)

S0 galaxies available images in SDSS DR8 CIG – Catalog of Isolated Galaxies

1500 < VRecession< 5500 km/s inclination < 70 LGG – Lyon Group of Galaxies

Hubble image; Drory & Fisher 2007

Hubble image; Drory & Fisher 2007

PS

EUD

OB

ULG

EC

LAS

SIC

AL

BU

LGE

AcknowledgementsThis research was made

possible due to the support of

the Wisconsin Space Grant

Consortium. Funds were

provided by the

Undergraduate Research

Award and the Undergraduate

Spring Scholarship Award

under NASA Training Grant

#NNX15AJ12H.

1. It has been proposed that galaxies

with bulge contribution Lbulge/Ltotal <

0.1 (10%) contain pseudobulges.

None of our galaxies meet this

criterion.

2. A less restrictive criterion contains the

proposal that all bulges characterized

by nbulge < 2.5 and Lbulge/Ltotal < 0.45

(45%) are pseudobulges; our CIG

(isolated) galaxy sample then contains

42% and our LGG (group) sample

68% pseudobulges.

For SOa/Sa/Sab galaxies the CIG

(isolated) sample contains 48% and

the LGG (group) sample 28%

pseudobulges. An isolated sample of

Sb/Sbc/Sc galaxies contains 94 %

pseudobulges using criterion 2.

For E galaxies, both the LGG (group)

sample and CIG (isolated) sample

contain 0% pseudobulges.

Rh/r

oeI)r(I

]1n/1)er/r[(nb

e10I)r(I

BUDDA Fortran Code (BUlge/Disk Decomposition Analysis)- de Souza et al. 2004

Disk: (Exponential profile)

Bulge and Bar: (Sérsic profile)

Bulge/Disk /Bar Image Decomposition

Io – central intensity

hR – radial scalelength

Ie - effective intensity

re – effective radius

n – Sérsic index

3 out of 12 (25%) of CIG

galaxies have bars.

12 out of 28 (43%) of LGG

galaxies have bars.

• Left Histograms: The LGG

(group) sample and CIG

(isolated) sample have

similar disk scalelengths

overall. However, galaxies

without bars have larger

disk scalelengths than

barred galaxies.

• Right Histograms: The

LGG (group) sample

galaxies are similar to the

CIG (isolated) sample

overall. Additionally, the

non-barred galaxies for

each sample are larger

than their barred

counterparts.0 2 4 6 8 10 12 14 16

0

4

8

12

16Mean: 2.79 0.21

Median: 2.66

LGG bar

Disk Radial Scalelength (kpc)

0 2 4 6 8 10 12 14 160

1

2

3

4

5Mean: 5.38 1.31

Median: 3.32

LGG

0 2 4 6 8 10 12 14 160

1

2

3

4

5Mean: 2.25 0.09

Median: 2.27

Nu

mbe

r o

f G

ala

xie

s

CIG bar

Comparison of Disk Radial Scalelength

for Barred and Non-Barred Galaxies

0 2 4 6 8 10 12 14 160

1

2

3

4

5Mean: 4.71 1.15

Median: 4.26

CIG

0.1 0.2 0.3 0.4 0.5 0.6 0.7

1

2

3

4

5

6

LGG (group galaxies)

CIG (isolated galaxies)

Se

rsic

Ind

ex o

f B

ulg

e (

nb

ulg

e)

Luminosity Ratio (Lbulge

/LTotal

)

Sersic Index vs Luminosity Ratio

5 10 15 20 25 30 35 40 45 50

-19

-20

-21

-22

-23

-24

LGG (group galaxies)

CIG (isolated galaxies)

Ab

so

lute

Mag

nitu

de

Diameter (kpc)

Absolute Magnitude vs Diameter

0.1 0.2 0.3 0.4 0.5 0.60

2

4

6

8 Mean: 0.26 0.02

Median: 0.25

Luminosity Ratio Lbulge

/LTotal

LGG barred

0.1 0.2 0.3 0.4 0.5 0.60

2

4

6

8Mean: 0.42 0.03

Median: 0.41

Nu

mbe

r o

f G

ala

xie

s

LGG

0.1 0.2 0.3 0.4 0.5 0.60

1

2Mean: 0.39 0.12

Median: 0.39

CIG barred

Comparison of Luminosity Ratio for

Barred and Non-Barred Galaxies

0.1 0.2 0.3 0.4 0.5 0.60

1

2

3

4Mean: 0.44 0.05

Median: 0.41

CIG

0 10 20 30 40 500

2

4

6

8 Mean: 17.34 1.87

Median: 15.40

Galaxy Diameter (kpc)

LGG barred

0 10 20 30 40 500

1

2

3

4

5Mean: 22.75 2.97

Median: 21.77

LGG

Comparison of Galaxy Diameter for

Barred and Non-Barred Galaxies

0 10 20 30 40 500

1

2

3Mean: 11.01 3.90

Median: 7.96

Num

ber

of G

ala

xie

s

CIG barred

0 10 20 30 40 500

2

4

6Mean: 20.62 3.04

Median: 17.70

CIG

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

4

8

12Mean: 0.54 0.05

Median: 0.52

Effective Radius of Bulge, re (kpc)

LGG barred

Comparison of Effective Radius of Bulge

for Barred and Non-Barred Galaxies

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

2

4

6

8Mean: 1.17 0.26

Median: 0.90

LGG

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

1

2

3Mean: 0.87 0.12

Median: 0.80

Nu

mbe

r o

f G

ala

xie

s

CIG barred

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

2

4

6

8Mean: 0.98 0.12

Median: 0.92

CIG

Conclusions and Future Work• Lenticular galaxies in group (nurtured) environments tend to have smaller bulges and a higher percentage of pseudobulges than those in

isolated environments. This difference is not noticeable for spiral morphological types. This might suggest that lenticular galaxies in group

environments are more likely to form secularly than isolated galaxies. Typically, galaxies in group environments form by mergers and isolated

form by secular evolution. This suggests that isolated lenticulars more likely have consumed all of their neighbors more recently. Another

possibility is that pseudobulges could also be formed by mergers for lenticular morphological types.

• Non-barred galaxies are larger and have more luminous bulges than barred galaxies, suggesting that bars take away material from the bulge

during the galaxy’s formation.

• The color of the galaxies correlates with the absolute magnitude.

• In the future, we could perform bulge-disk-bar decomposition of each galaxy in the g-band, and compare the colors for the bulges.

• Left Histograms: Compared

to CIG (isolated) galaxies,

the LGG (group) galaxy

bulges tend to be smaller

overall. Galaxies without

bars have larger bulges than

barred galaxies. This effect

is more prominent in the

LGG (group) sample.

• Right Histograms: The

luminosity ratio is smaller

overall for LGG (group)

galaxies compared to CIG

(isolated) galaxies. Galaxies

without bars have more

luminous bulges compared

to barred galaxies. In the

CIG (isolated) sample it is

unclear whether this is

meaningful, due to poor

statistics.

• Top Right Graph: Larger

galaxies tend to be more

luminous, while smaller

galaxies tend to be less

luminous.

• Middle Right Graph:

More luminous galaxies

are slightly bluer than

less luminous galaxies.

Isolated Galaxy (CIG) Galaxy in the Loose Group Sample (LGG)

Residual ImageOriginal Image - i band Total ModelPGC 5766

Bulge Model No BarDisk Model

Bar ModelDisk ModelBulge Model

Residual ImageOriginal Image - i band Total ModelPGC 53201

Pseudobulges are shaped

more like a disk, similar to

a miniature spiral galaxy.

Typically, galaxies with

pseudobulges form

through secular evolution.

Classical bulges are more

ellipsoidal in shape, similar

to a miniature elliptical

galaxy. Typically, galaxies

with classical bulges are

formed by mergers.

-19 -20 -21 -22 -23 -24

0.0

0.5

1.0

1.5

Color vs. Absolute Magnitude

LGG (group galaxies)

CIG (isolated galaxies)

Colo

r (g

-i)

Absolute Magnitude