Abstract - sarahparkerastro.com · Authors: Sarah Parker, Alyssa Likeness Faculty Mentor: Adriana...
Transcript of Abstract - sarahparkerastro.com · Authors: Sarah Parker, Alyssa Likeness Faculty Mentor: Adriana...
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