J/A+A/409/79 HELLAS2XMM survey. IV. (Fiore+, 2003)
The HELLAS2XMM survey. IV. Optical identifications and the evolution of the
accretion luminosity in the Universe.
Fiore F., Brusa M., Cocchia F., Baldi A., Carangelo N., Ciliegi P.,
Comastri A., La Franca F., Maiolino R., Matt G., Molendi S., Mignoli M.,
Perola G.C., Severgnini P., Vignali C.
<Astron. Astrophys. 409, 79 (2003)>
=2003A&A...409...79F 2003A&A...409...79F
ADC_Keywords: X-ray sources ; QSOs ;
Keywords: X-ray: background - X-ray: surveys - QSO: evolution
Abstract:
We present results from the photometric and spectroscopic
identification of 122 X-ray sources recently discovered by XMM-Newton
in the 2-10keV band (the HELLAS2XMM 1dF sample). Their flux cover the
range 8x10-15-4x10-13erg/cm2/s and the total area surveyed is
0.9 square degrees. One of the most interesting results (which is
found also in deeper surveys) is that about 20% of the hard X-ray
selected sources have an X-ray to optical flux ratio (X/O) ten times
or more higher than that of optically selected AGN. Unlike the faint
sources found in the ultra-deep Chandra and XMM-Newton surveys, which
reach X-ray (and optical) fluxes more than one order of magnitude
lower than the HELLAS2XMM survey sources, many of the extreme X/O
sources in our sample have R≲25 and are therefore accessible to
optical spectroscopy. We report the identification of 13 sources with
X/O≳10 (to be compared with 9 sources known from the deeper,
pencil-beam surveys). Eight of them are narrow line QSO (seemingly the
extension to very high luminosity of the type 2 Seyfert galaxies),
four are broad line QSO. The results from our survey are also used to
make reliable predictions about the luminosity of the sources not yet
spectroscopically identified, both in our sample and in deeper Chandra
and XMM-Newton samples. We then use a combined sample of 317 hard
X-ray selected sources (HELLAS2XMM 1dF, Chandra Deep Field North
1Msec, Chandra SSA13 and XMM-Newton Lockman Hole flux limited
samples), 221 with measured redshifts, to evaluate the cosmological
evolution of the hard X-ray source's number and luminosity densities.
Description:
We have obtained relatively deep (R=24-25) optical images for all 122
hard X-ray sources in the HELLAS2XMM 1dF sample using EFOSC2 at the
ESO 3.6 m telescope and DOLORES at the TNG. Exposures were typically
of 10min per image. Optical frames and X-ray images were brought to a
common astrometric reference frame using bright AGN (from 5 to 15 AGN
per field). Typical systematic shifts were of the order of 1", the
maximum shift was of ∼2".
Optical spectra of 97 of the 110 sources with optical counterparts
brighter than R=24 have been obtained using EFOSC2 at the ESO 3.6m
telescope and FORS1 at VLT/UT1 during 5 observing runs performed
between Jan. 2000 and Aug. 2002. A total of 9 nights at the 3.6m and
24h of VLT time have been devoted to this program.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 122 The HELLAS2XMM 1dF sample
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See also:
J/MNRAS/327/771 : BeppoSAX HELLAS survey. II. (Fiore+, 2001)
J/A+A/370/900 : BeppoSAX HELLAS survey. IV (Vignali+, 2001)
J/ApJ/570/100 : BeppoSAX HELLAS survey. V. (La Franca+, 2002)
J/MNRAS/342/575 : BeppoSAX HELLAS survey. VI. (Ciliegi, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID Source identification
10 A1 --- n_ID [abcdi] Note (1)
12- 13 I2 h RAh X-ray right ascension (J2000)
15- 16 I2 min RAm X-ray right ascension (J2000)
18- 21 F4.1 s RAs X-ray right ascension (J2000)
23 A1 --- DE- X-ray declination sign (J2000)
24- 25 I2 deg DEd X-ray declination (J2000)
27- 28 I2 arcmin DEm X-ray declination (J2000)
30- 31 I2 arcsec DEs X-ray declination (J2000)
34- 35 I2 h RAo.h ? Optical (R band) right ascension (J2000)
37- 38 I2 min RAo.m ? Optical (R band) right ascension (J2000)
40- 43 F4.1 s RAo.s ? Optical (R band) right ascension (J2000)
45 A1 --- DEo.- Optical (R band) declination sign (J2000)
46- 47 I2 deg DEo.d ? Optical (R band) declination (J2000)
49- 50 I2 arcmin DEo.m ? Optical (R band) declination (J2000)
52- 53 I2 arcsec DEo.s ? Optical (R band) declination (J2000)
55- 57 F3.1 arcsec Dist ? Separation between the X-ray and optical
positions
59- 63 F5.2 10-17W/m2 Fx 2-10keV flux (10-14erg/cm2/s)
65- 68 F4.1 mag Rmag R magnitude
70- 73 A4 --- Class Classification of the optical spectrum (2)
75 A1 --- n_Class [efgh] Note on Class (3)
78- 82 F5.3 --- z ? Redshift
84 A1 --- n_z [l] Note on redshift (4)
87- 91 F5.2 [10-7W] logLx ? 2-10keV luminosity
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Note (1): Notes on the object:
a = Group of galaxies in the error-box;
b = Near bright star;
c = Aperture photometry at the position of a bright K source
(Mignoli et al., 2003, in prep.)
d = Two possible counterparts;
i = Two possible counterparts, a type 1 AGN and an R-K6.1 object
(Brusa et al., 2003A&A...409...65B 2003A&A...409...65B, Mignoli et al. 2003 in prep.)
Note (2): Classification as follows:
AGN1 = AGN type 1
AGN2 = AGN type 2
ELG = Emission Line Galaxy
ETG = Early Type Galaxy
* = Star
Note (3): Note on the classification:
e = Classification tentative;
f = Two nearby objects, a type 2 AGN and an emission line galaxy,
at the same redshift;
g = Two nearby emission line galaxies at the same redshift;
h = Extended, emission from a group or cluster of galaxies,
z based on nearest galaxy;
Note (4): Note on redshift:
l = redshift tentative, based on a single faint line.
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Acknowledgements: F. Fiore <fiore(at)mporzio.astro.it>
References:
Baldi et al., Paper I 2002ApJ...564..190B 2002ApJ...564..190B
Comastri et al., Paper II 2002ApJ...571..771C 2002ApJ...571..771C
Brusa et al., Paper III 2003A&A...409...65B 2003A&A...409...65B
(End) Patricia Bauer [CDS] 07-Oct-2003