J/MNRAS/442/533 Recently quenched elliptical galaxies in SDSS (McIntosh+, 2014)
A new population of recently quenched elliptical galaxies in the SDSS.
McIntosh D.H., Wagner C., Cooper A., Bell E.F., Keres D.,
van den Bosch F.C., Gallazzi A., Haines T., Mann J., Pasquali A.,
Christian A.M.
<Mon. Not. R. Astron. Soc., 442, 533-557 (2014)>
=2014MNRAS.442..533M 2014MNRAS.442..533M
ADC_Keywords: Galaxy catalogs ; Morphology
Keywords: galaxies: elliptical and lenticular, cD - galaxies: evolution -
galaxies: formation - galaxies: star formation
Abstract:
We use the Sloan Digital Sky Survey to investigate the properties of
massive elliptical galaxies in the local Universe (z≤0.08) that have
unusually blue optical colours. Through careful inspection, we
distinguish elliptical from non-elliptical morphologies among a large
sample of similarly blue galaxies with high central light
concentrations (cr≥2.6). These blue ellipticals comprise 3.7 per
cent of all c_r≥2.6 galaxies with stellar masses between 1010 and
1011h-2M☉. Using published fibre spectrum diagnostics, we
identify a unique subset of 172 non-star-forming ellipticals with
distinctly blue urz colours and young (<3Gyr) light-weighted stellar
ages. These recently quenched ellipticals (RQEs) have a number density
of 2.7-4.7x10-5h3/Mpc3 and sufficient numbers above
2.5x1010h-2M☉ to account for more than half of the expected
quiescent growth at late cosmic time assuming that this phase lasts
0.5Gyr. RQEs have properties that are consistent with a recent merger
origin (i.e. they are strong 'first-generation' elliptical
candidates), yet few involved a starburst strong enough to produce an
E+A signature. The preferred environment of RQEs (90 per cent reside
at the centres of <3x1012h-1M☉ groups) agrees well with the
'small group scale' predicted for maximally efficient spiral merging
on to their halo centre and rules out satellite-specific quenching
processes. The high incidence of Seyfert and LINER activity in RQEs
and their plausible descendants may heat the atmospheres of small host
haloes sufficiently to maintain quenching.
Description:
The primary goal of this study is to identify and analyse high-mass
elliptical (pure-spheroid) galaxies at low redshift that are plausibly
transitioning redwards. To isolate a statistical sample of such
galaxies that is mass-limited, volume-limited and has high
spectroscopic completeness, we employ the SDSS Main Galaxy Sample
(MGS; Strauss et al. 2002AJ....124.1810S 2002AJ....124.1810S) and apply the following
three-step selection: (1) isolate a large sample of blue-cloud
galaxies with redshifts z≤0.08 and stellar masses bracketing the
bimodal mass scale of 3x1010M☉, (2) apply an automated
high-concentration cut to identify the bulge-dominated subset
(hereafter blue ETGs) and (3) visually distinguish elliptical galaxies
from other more dominant morphologies found in the blue ETG population
(e.g. spiral and disc galaxies with prominent bulges).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 64 172 Catalog of recently quenched ellipticals (RQEs)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NYU]
4- 10 I7 --- NYU NYUID galaxy identification number from
NYU-VAGC (Blanton et al. 2005AJ....129.2562B 2005AJ....129.2562B)
13- 24 F12.8 deg RAdeg Right ascension (J2000) from SDSS
27- 37 F11.8 deg DEdeg Declination (J2000) from SDSS
39- 46 F8.6 --- zsp [0.01/0.08] SDSS spectroscopic redshift, from
the NYU-VAGC (2005AJ....129.2562B 2005AJ....129.2562B)
48- 53 F6.3 [Msun] logM* [10/11.2] Stellar mass estimates (1)
55- 56 A2 --- Type [pE E] Visual classification type (2)
58- 64 A7 --- EType Optical emission type (3)
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Note (1): in units of log10(h-2M☉) based on SDSS Petrosian photometry
and Bell et al. (2003ApJS..149..289B 2003ApJS..149..289B) M/L ratios.
Note (2): Visual classification type (see section 2.2.2 for details):
E = Elliptical or spheroidal galaxies with bright centres and smooth light
profiles showing little or no asymmetric features
pE = Peculiar elliptical galaxies with one or more of the following
morphological disturbances consistent with recent tidal activity:
excess outer light, asymmetric outer isophotes, shells, asymmetric
dustlane, blue core or clearly dust-reddened core
Note (3): Optical emission type (see section 3.2 for details):
LINER = LINER type (Low-Ionization Nuclear Emission-line Region)
Quies = Quiescent type
Seyfert = Seyfert type
Y06 = LINER based on the Yan et al. (2006ApJ...648..281Y 2006ApJ...648..281Y) criteria
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Feb-2015