J/A+A/662/A54 X-ray detected sources around Spiderweb Galaxy (Tozzi+, 2022)
The 700 ks Chandra Spiderweb Field.
I. Evidence for widespread nuclear activity in the protocluster.
Tozzi P., Pentericci L., Gilli R., Pannella M., Fiore F., Miley G.,
Nonino M., Rottgering H.J.A., Strazzullo V., Anderson C.S., Borgani S.,
Calabro A., Carilli C., Dannerbauer H., Di Mascolo L., Feruglio C.,
Gobat R., Jin S., Liu A., Mroczkowski T., Norman C., Rasia E., Rosati P.,
Saro A.
<Astron. Astrophys., 662, A54 (2022)>
=2022A&A...662A..54T 2022A&A...662A..54T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; X-ray sources
Keywords: galaxies: clusters: general - galaxies: active -
X-rays: galaxies: clusters
Abstract:
We present an analysis of the 700ks Chandra ACIS-S observation of the
field around the radio galaxy J1140-2629 (the Spiderweb Galaxy) at
z=2.156, focusing on the nuclear activity in the associated
large-scale environment.
We identified unresolved X-ray sources in the field down to flux
limits of 1.3x10-16 and 3.9x10-16erg/s/cm2 in the soft
(0.5-2.0keV) and hard (2-10keV) band, respectively. We searched for
counterparts in the optical, near-infrared, and submillimeter catalogs
available in the literature to identify X-ray sources belonging to the
protocluster and derived their X-ray properties.
We detect 107 X-ray unresolved sources within 5 arcmin (corresponding
to 2.5Mpc) of J1140-2629, among which 13 have optical counterparts
with spectroscopic redshift 2.11<z<2.20, and 1 source has a
photometric redshift consistent with this range. The X-ray-emitting
protocluster members are distributed approximately over a
∼3.2x1.3Mpc2 rectangular region. An X-ray spectral analysis for all
the sources within the protocluster shows that their intrinsic
spectral slope is consistent with an average <Γ≳1.84±0.04.
Excluding the Spiderweb Galaxy, the best-fit intrinsic absorption for
five protocluster X-ray members is NH>1023cm-2, while another
six have upper limits of the order of a few times 1022cm-2. Two
sources can only be fitted with very flat Γ≤1, and are
therefore considered Compton-thick candidates. The 0.5-10keV
rest-frame luminosities of the 11 Compton-thin protocluster members
corrected for intrinsic absorption are greater than 2x1043erg/s.
These values are typical for the bright end of a Seyfert-like
distribution and significantly greater than X-ray luminosities
expected from star formation activity. The X-ray luminosity function
of the AGN in the volume associated to the Spiderweb protocluster in
the range 1043<LX<1044.5erg/s is at least ten times higher than
that in the field at the same redshift and significantly flatter,
implying an increasing excess at the bright end. The X-ray AGN
fraction is measured to be 25.5±4.5% of the spectroscopically
confirmed members in the stellar mass range log(M*/M☉)>10.5.
This value corresponds to an enhancement factor of
6.0-3.0+9.0for the nuclear activity with
L0.5-10keV>4x1043erg/s with respect to the COSMOS field at
comparable redshifts and stellar mass range.
We conclude that the galaxy population in the Spiderweb protocluster
is characterized by enhanced X-ray nuclear activity triggered by
environmental effects on megaparsec scales.
Description:
In this paper, we focus on the field of view within a radius of 5
arcmin (corresponding to ∼2.5Mpc at z=2.156) centered on the
nucleus of the Spiderweb, which results in a total of 78.5 arcmin2.
This region includes the solid angle covered by our observation with a
sensitivity that is greater than about half of the highest sensitivity
reached at the aimpoint, and with an angular resolution that is higher
than 3 arcsec (FWHM). This allows us to have a smooth sky coverage,
thereby avoiding large corrections when evaluating the number counts.
We identify 107 X-ray sources within a radius of 5 arcmin centered on
the Spiderweb Galaxy, down to flux limits of 1.3x10-16erg/s/cm2
and 3.9x10-16erg/s/cm2 in the soft and hard band, respectively. We
compute the cumulative number counts which are found to be consistent
with results from X-ray deep fields in the literature.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 77 107 Catalog of the X-ray detected sources within
5 arcmin from the Spiderweb Galaxy
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- XID [1/107] Seqiential number
4- 5 A2 --- n_XID Note on XID (1)
7- 15 F9.5 deg RAdeg Centroid of the X-ray detected emission
right ascension (J2000)
17- 25 F9.5 deg DEdeg Centroid of the X-ray detected emission
declination (J2000)
27- 32 F6.1 ct/s CRS Count-rate in soft (0.5-2.0keV) band
34- 37 F4.1 ct/s e_CRS rms uncertainty on CRS
39- 44 F6.1 ct/s CRH Count-rate in hard (2-10keV) band
46- 49 F4.1 ct/s e_CRH rms uncertainty on CRH
51 A1 --- l_FS Limit flag on FW (2)
52- 57 F6.2 10-19W/m2 FS Flux in soft (0.5-2.0keV) band
59- 63 F5.2 10-19W/m2 e_FS ? rms uncertainty on FS
65 A1 --- l_FH Limit flag on FH (2)
66- 71 F6.1 10-19W/m2 FH Flux in hard (2-10keV) band
73- 77 F5.1 10-19W/m2 e_FH ? rms uncertainty on FH
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Note (1): For sources with extraction radius smaller than rext as defined
in Section 5.1, as follows:
r1 = Sources with apex an extraction radius of 1 pixel
r3 = Sources with apex an extraction radius of 3 pixels
Note (2): If a source does not satisfy S/N>2 in one band, we report the
2σ upper limit.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Feb-2023