J/MNRAS/453/3729 Sersic + exponential disc morphologies in Coma (Head+, 2015)
Beyond Sersic + exponential disc morphologies in the Coma Cluster.
Head J.T.C.G., Lucey J.R., Hudson M.J.
<Mon. Not. R. Astron. Soc., 453, 3729-3753 (2015)>
=2015MNRAS.453.3729H 2015MNRAS.453.3729H (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Morphology
Keywords: galaxies: clusters: individual: Abell 1656 -
galaxies: elliptical and lenticular, cD - galaxies: evolution -
galaxies: formation - galaxies: structure
Abstract:
Galaxies are not limited to simple spheroid or bulge + disc
morphologies. We explore the diversity of internal galaxy structures
in the Coma Cluster across a wide range of luminosities (-17>Mg>-22)
and cluster-centric radii (0<rcluster<1.3r200) through
analysis of deep Canada-France-Hawaii Telescope i-band imaging.
We present 2D multicomponent decomposition via galfit, encompassing a
wide range of candidate model morphologies with up to three
photometric components. Particular focus is placed on early-type
galaxies with outer discs (i.e. S0s), and deviations from simple
('unbroken') exponential discs. Rigorous filtering ensures that each
model component provides a statistically significant improvement to
the goodness-of-fit. The majority of Coma Cluster members in our
sample (478 of 631) are reliably fitted by symmetric structural
models. Of these, 134 (28 percent) are single Sersic objects, 143
(30 percent) are well-described by 2-component structures, while 201
(42 percent) require more complex models. Multicomponent Sersic
galaxies resemble compact pseudo-bulges (n∼2, Re∼4kpc) surrounded by
extended Gaussian-like outer structures (Re>10kpc). 11 percent of
galaxies (N=52) feature a break in their outer profiles,
indicating 'truncated' or 'antitruncated' discs. Beyond the break
radius, truncated galaxies are structurally consistent with
exponential discs, disfavouring physical truncation as their formation
mechanism. Bulge luminosity in antitruncated galaxies correlates
strongly with galaxy luminosity, indicating a bulge-enhancing origin
for these systems. Both types of broken disc are found overwhelmingly
(>70 percent) in 'barred' galaxies, despite a low measured bar
fraction for Coma (20±2 percent). Thus, galaxy bars play an
important role in formation of broken disc structures. No strong
variation in galaxy structure is detected with projected
cluster-centric radius.
Description:
This study makes use of the data as previously described in Paper I
(Head et al., 2014, Cat. J/MNRAS/440/1690). To recap: optical imaging
covering a total of 9 deg2 of the Coma Cluster in the i band was
acquired using the MegaCam instrument on the 3.6 m CFHT during 2008
March-June (run ID 2008AC24, PI: M. Hudson). Total (co-added)
exposure times of 300 s were obtained for each observed field,
yielding ∼12 x deeper imaging data (from D2texp) compared to SDSS
(2.5m telescope, 53s exposures). The MegaCam frames were
sky-subtracted during pre-processing using a 64 pixel mesh. A point
spread function (psf) full width at half-maximum of between 0.65 and
0.84-arcsec was typical. The pixel scale was ∼0.186arcsec/pix.
In this work, we fit galaxies with a range of analytical models in
order to thoroughly explore the diversity of internal galaxy
structures.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablec1.dat 222 631 The structural and photometric parameters of
multicomponent models fits (i band) for the
entire galaxy sample
--------------------------------------------------------------------------------
See also:
J/MNRAS/440/1690 : Bulge and disc colours of ETG in Coma (Head+, 2014)
Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- ID SDSS DR8 object ID
21- 27 F7.3 deg RAdeg Right ascension (J2000)
29- 34 F6.3 deg DEdeg Declination (J2000)
36- 40 F5.3 --- z SDSS redshift
42- 48 F7.3 mag iMAG Total rest-frame i-band magnitude
50- 56 F7.3 kpc Rtot Upper limit total half-light radius
(exponential scalelength)
58- 64 F7.3 mag iMAG1 Component 1 (exponential disk) rest-frame
total i-band magnitude
66- 71 F6.3 kpc R1 Component 1 (exponential disk) half-light
radius (exponential scalelength
73- 78 F6.3 --- n1 Component 1 (exponential disk) Sersiec index
80- 84 F5.3 --- q1 Component 1 (exponential disk) axis ratio (b/a)
86- 92 F7.3 deg PA1 ?=999 Component 1 (exponential disk)
position angle
94- 98 F5.3 --- C0 ?=999 Component 1 (exponential disk)
boxiness/disciness parameter
100-106 F7.3 mag iMAG2 ?=999 Component 2 (Bulge) rest-frame total
i-band magnitude
108-114 F7.3 kpc R2 ?=999 Component 2 (Bulge) effective half-light
radius
116-122 F7.3 --- n2 ?=999 Component 2 (Bulge) Sersic index
124-130 F7.3 --- q2 ?=999 Component 2 (Bulge) axis ratio (b/a)
132-138 F7.3 deg PA2 ?=999 Component 2 (Bulge) position angle
140-146 F7.3 mag iMAG3 ?=999 Component 3 (boxy Sersics) rest-frame
total i-band magnitude
148-154 F7.3 kpc R3 ?=999 Component 3 (boxy Sersics) effective
half-light radius
156-162 F7.3 --- n3 ?=999 Component 3 (boxy Sersics) sersic index
164-170 F7.3 --- q3 ?=999 Component 3 (boxy Sersics) axis ratio
(b/a)
172-178 F7.3 deg PA3 ?=999 Component 3 (boxy Sersics) position angle
180-186 F7.3 kpc Rout Outer disc half-light radius
(exponential scalelength
188-194 F7.3 kpc Rbrk Disc Break radius
196-200 F5.3 --- CT1 Component 1 (exponential disk) light fraction
202-206 F5.3 --- CT2 Component 2 (Bulge) light fraction
208-212 F5.3 --- CT3 Component 3 (boxy Sersics) light fraction
214-217 A4 --- Mod Best-fitting model
219 I1 --- Profile [1/6] (B/D) type
Allen et al. (2006MNRAS.371....2A 2006MNRAS.371....2A)
221-222 I2 --- Flag [0/23] Fitting flag
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Head et al., paper I 2014MNRAS.440.1690H 2014MNRAS.440.1690H, Cat. J/MNRAS/440/1690
(End) Patricia Vannier [CDS] 08-Apr-2016