J/ApJ/681/1017 Chandra observations of lens groups (Fassnacht+, 2008)
The X-ray properties of moderate-redshift galaxy groups selected by association
with gravitational lenses.
Fassnacht C.D., Kocevski D.D., Auger M.W., Lubin L.M., Neureuther J.L.,
Jeltema T.E., Mulchaey J.S., McKean J.P.
<Astrophys. J., 681, 1017-1034 (2008)>
=2008ApJ...681.1017F 2008ApJ...681.1017F
ADC_Keywords: X-ray sources ; Clusters, galaxy ; Redshifts
Keywords: galaxies: clusters: general - gravitational lensing -
X-rays: galaxies: clusters
Abstract:
We present results from a systematic investigation of the X-ray
properties of a sample of moderate-redshift (0.3<z<0.6) galaxy
groups. These groups were selected not by traditional X-ray or optical
search methods, but rather by an association, either physical or along
the line of sight, with a strong gravitational lens. We calculate the
properties of seven galaxy groups in the fields of six lens systems.
Diffuse X-ray emission from the intragroup medium is detected in four
of the groups. All of the detected groups have X-ray luminosities
greater than 1042h-2ergs/s and lie on the LX-σv_^
relations defined by local groups and clusters. The upper limits for
the nondetections are also consistent with the local LX-σv_^
relationships. Although the sample size is small and deeper optical
and X-ray data are needed, these results suggest that lens-selected
groups are similar to X-ray-selected samples and thus are more massive
than the typical poor-group environments of local galaxies.
Description:
The systems analyzed for this paper are all strong lenses for which we
have obtained new observations with Chandra or for which data are
available in the Chandra archive. Observation parameters as follows:
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Target ObsID Exp (s) Obs.Date PI
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B0712 4199 97742 2004/12/17 Fassnacht
PG 1115 363 26489 2000/06/02 Garmire
B1422 367 16888a 2000/06/02 Garmire
B1600 3460 30176 2003/10/07 Kochanek
B1608 3461 29717 2003/09/09 Kochanek
B2108 6971 45507 2006/07/14 Fassnacht
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a = Reduced from 28429s due to flaring events.
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
group.dat 99 8 Properties of diffuse group emission (tables 2
and 3 of the paper)
table6.dat 69 51 Serendipitous sources detected in the field of
B0712+472
table7.dat 69 34 Serendipitous sources detected in the field of
B2108+213
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/ApJ/658/865 : Redshifts of galaxies in X-ray-luminous groups (Jeltema+,
2007)
J/ApJ/496/39 : Properties of poor groups of galaxies. I. (Zabludoff+ 1998)
Byte-by-byte Description of file: group.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Group Group name
10- 11 I2 h RAh ? Hour of right ascension (J2000)
13- 14 I2 min RAm ? Minute of right ascension (J2000)
16- 19 F4.1 s RAs ? Second of right ascension (J2000)
21 A1 --- DE- ? Declination sign (J2000)
22- 23 I2 deg DEd ? Degree of declination (J2000)
25- 26 I2 arcmin DEm ? Arcminute of declination (J2000)
28- 29 I2 arcsec DEs ? Arcsecond of declination (J2000)
31- 34 F4.1 10+20cm-2 nH Neutral hydrogen column densities of
Dickey & Lockman (1990ARA&A..28..215D 1990ARA&A..28..215D)
36- 38 I3 --- Cts ? Net counts in x-ray
40- 43 F4.2 10-3/s CtR ? Count rate in x-ray
45 A1 --- l_Flux Limit flag on Flux
46- 49 F4.1 aW/m2 Flux Soft band flux corrected from Galactic
absorption (1)
51- 53 F3.1 aW/m2 e_Flux ? Uncertainty in Flux
55 A1 --- l_Lx Limit flag on Lx
56- 59 F4.2 10+35W Lx Rest-frame bolometric luminosity in
1042h-2ergs/s units
61- 64 F4.2 10+35W e_Lx ? Uncertainty in Lx
66 A1 --- l_Lx500 Limit flag on Lx500
67- 70 F4.1 --- Lx500 ? Rest-frame bolometric luminosity
within R500 (in 1042h-2ergs/s)
72- 74 F3.1 --- e_Lx500 ? Uncertainty in Lx500
76- 77 I2 --- N ? Group optical number of members
78 A1 --- n_N [a] a = optical data in B2108-1 are for B2108
80- 84 F5.3 --- z ? Group optical redshift
86- 88 I3 km/s sigma ? Group optical radial velocity dispersion
90- 91 I2 km/s e_sigma ? σ uncertainty
93- 95 I3 kpc R500 ? Group optical radius at 500 times
critical density, in h-1kpc units (2)
97- 99 I3 arcsec the500 ? Group optical position angle at 500
times critical density
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Note (1): We determined the soft-band flux of the group emission by
normalizing a Raymond-Smith spectral model in the CIAO package Sherpa
to the net counts detected above the background in each system.
Units are 10-15erg/cm2/s = aW/m2.
Note (2): The value of R500 for each system was estimated from the radial
velocity dispersion that had been determined from the group galaxy
redshifts as R500=2σv/[500H(z)^0.5]
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Byte-by-byte Description of file: table6.dat table7.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [CXO]
5- 20 A16 --- CXO Name (JHHMMSS.s+DDMMSS,
in Simbad)
21 A1 --- f_CXO [b] extended source flag
23- 31 F9.5 deg RAdeg Right ascension in decimal degree (J2000)
33- 40 F8.5 deg DEdeg Declination in decimal degree (J2000)
42- 45 I4 ct Scts Soft (0.5-2.0keV) band net counts
47- 49 I3 ct Hcts Hard (2.0-8.0keV) band net counts
51- 54 I4 ct Fcts Full (0.5-8.0keV) band net counts
56- 59 F4.1 --- Ssig Soft (0.5-2.0keV) band significance (3)
61- 64 F4.1 --- Hsig Hard (2.0-8.0keV) band significance (3)
66- 69 F4.1 --- Fsig Full (0.5-8.0keV) band significance (3)
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Note (3): The significances are calculated as the net counts from each
source divided by the error of the background counts in the
measurement aperture.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 27-Oct-2010