J/ApJ/874/54 X-ray sources in the USS 1558-003 protocluster (Macuga+, 2019)
The fraction of active galactic nuclei in the USS 1558-003 protocluster
at z=2.53.
Macuga M., Martini P., Miller E.D., Brodwin M., Hayashi M., Kodama T.,
Koyama Y., Overzier R.A., Shimakawa R., Tadaki K.-I., Tanaka I.
<Astrophys. J., 874, 54 (2019)>
=2019ApJ...874...54M 2019ApJ...874...54M
ADC_Keywords: X-ray sources; Clusters, galaxy; Active gal. nuclei
Keywords: galaxies: active ; galaxies: clusters: general ; X-rays: galaxies ;
X-rays: galaxies: clusters ; X-rays: general
Abstract:
The incidence of active galactic nuclei (AGNs) within the local
environment is a potentially valuable probe of the mechanisms that
trigger and provide fuel for accretion onto supermassive black holes.
While the correlation between AGN fraction and environment has been
well-studied in the local universe, AGN fractions have been measured
for relatively few dense environments at high redshift. In this paper,
we present a measurement of the X-ray AGN fraction in the USS 1558-003
protocluster associated with the z=2.53 radio galaxy 4C-00.62. Our
measurement is based on a 100-ks Chandra observation, follow-up
spectroscopy from the Multi-Object Double Spectrograph on the Large
Binocular Telescope, and broad and narrowband photometry. These data
are sensitive to AGNs more luminous than LX>2x1043erg/s in the
rest-frame hard X-ray band (2-10keV). We have identified two X-ray
AGNs at the redshift of USS 1558-003, one of which is the radio
galaxy. We have determined that 2.0-1.3+2.6% of the Hα
emitters in the protocluster are X-ray AGNs. Unlike most other
high-redshift cluster progenitors studied with similar techniques,
USS1558-003 does not have a significantly higher fraction of AGNs than
field galaxies at similar redshifts. This lower AGN fraction is
inconsistent with the expectation that the higher gas fractions at
high redshift, combined with the high galaxy densities and modest
relative velocities in protoclusters, should produce higher AGN fractions.
Description:
We observed the USS 1558-003 protocluster with the Chandra ACIS-I
camera in 2014 June. The X-ray images were split into two exposures of
approximately 63ks (ObsID 16160) and 37ks (ObsID 16619) for a total
integration of about 100ks.
We adopted a Galactic neutral Hydrogen column density of
NH=7.83x1020/cm2 and a power-law index of Γ=1.7 to
calculate the fluxes of the 126 identified X-ray sources (see Table 1).
We also obtained deep, multi-slit spectroscopy of a subset of these
X-ray sources with the Multi-Object Double Spectrograph (MODS) on the
Large Binocular Telescope (LBT) in 2015 April and May to determine if
they are at the protocluster redshift. See Section 2.2 for further
explanations.
Objects:
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RA (ICRS) DE Designation(s)
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16 01 17.0 -00 28 48 USS 1558-003 = NAME USS 1558-003 Protocluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 126 X-ray sources
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
J/ApJ/592/728 : Lyman break galaxies at redshift z∼3 (Steidel+, 2003)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/ApJ/701/587 : Deep HST H-band survey. II. QUEST QSOs (Veilleux+, 2009)
J/ApJ/761/114 : Multi-wavelength study of clusters of gal. II. (Atlee+, 2012)
J/ApJ/765/87 : Chandra obs. of the 2QZ Cluster 1004+00 (Lehmer+, 2013)
J/MNRAS/428/1128 : UDS/COSMOS HiZELS galaxies (Sobral+, 2013)
J/ApJ/825/72 : Follow-up study of AGNs in z>1 clusters (Alberts+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 deg RAdeg [240.14/240.46] Right Ascension (J2000)
9- 14 F6.3 deg DEdeg [-0.76/-0.31] Declination (J2000)
16- 22 F7.3 ct NetCts [6.991/617.102] Net photon counts
24- 32 E9.3 mW/m2 Flux [8.8e-16/8.4e-14] X-ray flux in 0.5-7keV band
34- 42 E9.3 mW/m2 e_Flux [3.4e-16/4.3e-15] Error in Flux
44 A1 --- Mm [yn] Confirmation as cluster member
("y" = 2 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Aug-2020