J/ApJ/790/16 X-ray ETGs properties in the Chandra COSMOS survey (Civano+, 2014)
Early-type galaxies in the Chandra COSMOS survey.
Civano F., Fabbiano G., Pellegrini S., Kim D.-W., Paggi A., Feder R.,
Elvis M.
<Astrophys. J., 790, 16 (2014)>
=2014ApJ...790...16C 2014ApJ...790...16C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; X-ray sources ; Redshifts
Keywords: galaxies: evolution - galaxies: formation - surveys - X-rays: galaxies
Abstract:
We study a sample of 69 X-ray detected early-type galaxies (ETGs),
selected from the Chandra COSMOS survey, to explore the relation
between the X-ray luminosity of hot gaseous halos (L_X, gas_) and the
integrated stellar luminosity (LK) of the galaxies, in a range of
redshift extending out to z = 1.5. In the local universe, a tight,
steep relationship has been established between these two quantities
(Lx.gas ∼ LK4.5), suggesting the presence of largely virialized
halos in X-ray luminous systems. We use well-established relations
from the study of local universe ETGs, together with the expected
evolution of the X-ray emission, to subtract the contribution of
low-mass X-ray binary populations from the X-ray luminosity of our
sample. Our selection minimizes the presence of active galactic nuclei
(AGNs), yielding a sample representative of normal passive COSMOS
ETGs; therefore, the resulting luminosity should be representative of
gaseous halos, although we cannot exclude other sources such as
obscured AGNs or enhanced X-ray emission connected with embedded star
formation in the higher-z galaxies. We find that most of the galaxies
with estimated LX< 1042 erg/s and z < 0.55 follow the L_X,
gas-LK_ relation of local universe ETGs. For these galaxies, the
gravitational mass can be estimated with a certain degree of
confidence from the local virial relation. However, the more luminous
(1042 erg/s <LX< 1043.5 erg/s) and distant galaxies present
significantly larger scatter; these galaxies also tend to have younger
stellar ages. The divergence from the local L_X, gas-LK_relation in
these galaxies implies significantly enhanced X-ray emission up to a
factor of 100 larger than predicted from the local relation. We
discuss the implications of this result for the presence of hidden
AGNs, and the evolution of hot halos, in nuclear and star formation
feedback.
Description:
The galaxies in our sample were selected from the C-COSMOS X-ray
source identification catalog (Civano et al. 2012, J/ApJS/201/30) to
have a rest-frame X-ray luminosity of LX < 5 x 1043 erg/s in
the 0.5-10 keV band (using the spectral assumptions in Elvis et al.
2009, J/ApJS/184/158) and to be classified as elliptical or S0 from
their optical to near-infrared spectral energy distribution (SED). Of
the 69 galaxies in the X-ray ETG sample, 53 have spectroscopic
redshifts. For the remaining 16 galaxies, we used the available
photometric redshifts reported in the C-COSMOS identification catalog
(Civano et al. 2012, J/ApJS/201/30; Salvato et al. 2011,
J/ApJ/742/61). Given the high quality of the photometry available for
the sources in the COSMOS field (see Salvato et al. 2011,
J/ApJ/742/61), we are confident that we can use photometric redshifts
when spectroscopic ones are not available. Although not uniform, an
optical spectroscopic classification is available for the C-COSMOS
sources (see Civano et al. 2012, J/ApJS/201/30 for the details on
observing programs). According to the spectroscopic classification,
our sample includes 24 absorption line galaxies (ALGs) and 29 narrow
emission line (NL) objects. Moreover, using standard diagnostic
diagrams (Bongiorno et al. 2010, J/A+A/510/A56), we find that of the
29 NL sources, 5 are classified as NL active galactic nuclei (i.e.,
Type 2 AGNs) and 7 as star-forming galaxies, while 17 spectra remain
unclassified.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 69 COSMOS X-Ray ETGs Properties
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See also:
J/MNRAS/328/461 : X-ray luminosities of early-type galaxies (O'Sullivan+, 2001)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/A+A/510/A56 : zCOSMOS type-2 AGN (Bongiorno, 2010)
J/ApJ/725/480 : Stellar X-ray sources in the COSMOS survey (Wright+, 2010)
J/ApJ/742/61 : Photometric redshift of AGNs from XMM- and C-COSMOS
(Salvato+ 2011)
J/ApJS/201/30 : The Chandra COSMOS survey. III. (Civano+, 2012)
J/MNRAS/422/494 : X-ray properties of optically selected ETGs
(Danielson+, 2012)
J/ApJ/819/62 : The COSMOS-Legacy Survey (CLS) catalog (Civano+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- CID Chandra identifier according to Elvis
et al. (2009, Cat. J/ApJS/184/158)
[ECV2009] NNNNN in Simbad
6- 10 F5.3 --- z Redshift
11 A1 --- n_z [d] Note on z (1)
13- 18 A6 --- MType Spectral type (2)
20- 27 E8.3 ct/s CR Count rates in the 0.5-7 keV band
29- 35 E7.3 ct/s e_CR Error in count rates
37- 41 F5.2 [10-7W] logL(X-lmxb) Log of the X-ray luminosity in the
0.3-8 keV band (3)
43- 47 F5.2 [10-7W] logL(X) Log of the remaining X-ray luminosity in
the 0.3-8 keV band (4)
49 A1 --- l_HR Limit flag on HR
50- 54 F5.2 --- HR Hardness ratio (5)
56- 57 I2 --- Ext [0/10] Extension of X-ray emission
59- 63 F5.2 [Lsun] logL(K) Log of K band luminosity
65- 68 F4.2 [Lsun] e_logL(K) Error in logL(K)
70- 74 F5.2 [Msun] logM* Log of stellar mass
76- 80 E5.1 Gyr Age Age of early type galaxy
82 I1 --- Group [1]?=- Group relevance
84 I1 --- Radio [1]?=- Radio emission flag
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Note (1): d for Photometric redshift.
Note (2): Spectral type as follows :
ALG = absorption line galaxies
NL = narrow emission line
NLAGN = NL active galactic nuclei
SF gal = star forming galaxies
Note (3): X-lmxb is the X-ray luminosity computed using Fragos et al.
(2013ApJ...776L..31F 2013ApJ...776L..31F) relation.
Note (4): LX is the remaining X-ray luminosity after subtracting the LMXB
contribution to the total and it is computed using a thermal model as in
Section 3.1.
Note (5): defined as HR = (H-S/H+S), where H and S are the number of
net counts in the hard band (2-7 keV) and soft band (0.5-2 keV), respectively,
to study the spectral shape of the sources.
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 16-Mar-2017