J/ApJ/876/53ivo://CDS.VizieR/J/ApJ/876/53doi:10.26093/cds/vizier.18760053CDSJin X.Hou M.Zhu Z.Li Z.2021-03-26T07:19:13Z2020-10-27T13:26:49ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxy-clustersx-ray-sourcesBased on archival Chandra observations with a total exposure of 1.3Ms, we study X-ray point sources in the Fornax cluster of galaxies, with the primary aim of searching for intracluster X-ray source populations. We detect 1177 point sources out to a projected radius of ~30' (~180kpc) from the cluster center and down to a limiting 0.5-8keV luminosity of ~3x10^37^erg/s. We construct the source surface density profile, after excluding sources associated with foreground stars, known globular clusters, ultra-compact dwarfs, and galactic nuclei. From this profile we statistically identify ~183 excess sources that are not associated with the bulk stellar content of the individual member galaxies of Fornax, nor with the cosmic X-ray background. Taking into account Poisson error and cosmic variance, the cumulative significance of this excess is at the >~2{sigma} level (with a maximum of 3.6{sigma}) outside three effective radii of the central giant elliptical, NGC 1399. The luminosity function of the excess sources is found to be significantly steeper than that of the GC-hosting sources (presumably low-mass X-ray binaries (LMXBs)), disfavoring the possibility that unidentified GCs are primarily responsible for the excess. We show that a large fraction of the excess can be related to the extended stellar halo of NGC 1399 and/or the diffuse intracluster light, thus providing strong evidence for the presence of intracluster X-ray sources in Fornax, the second unambiguous case for a galaxy cluster after Virgo. Other possible origins of the excess, including supernova-kicked LMXBs and stripped nucleated dwarf galaxies are discussed.2019ApJ...876...53Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/876/53CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2014)I/284 : The USNO-B1.0 Catalog (Monet+ 2003)VII/180 : Galaxies in Fornax Cluster and five nearby groups (Ferguson+ 1990)J/MNRAS/344/188 : BVI photometry in Fornax cluster galaxies (Karick+, 2003)J/ApJS/153/223 : ACS Virgo Cluster Survey. I. (Cote+, 2004)J/ApJS/169/213 : ACS Fornax Cluster Survey. I. (Jordan+, 2007)J/ApJS/169/401 : ChaMP X-ray point source catalog (Kim+, 2007)J/AJ/137/498 : UCD and bright GC in Fornax (Gregg+, 2009)J/ApJ/706/223 : X-ray point sources near the Galactic Center (Hong+, 2009)J/ApJ/721/1368 : X-ray emission from the Sombrero galaxy (Li+, 2010)J/ApJ/736/90 : Chandra X-ray sources of NGC 1399 (Paolillo+, 2011)J/A+A/533/A33 : LMXBs detected in nearby galaxies (Zhang+, 2011)J/A+A/547/A65 : Extended stellar objects in galaxies (Bruens+, 2012)J/ApJ/763/40 : UBVI photom. of GCs in the Fornax galaxy cluster (Kim+, 2013)J/ApJS/221/13 : ACS Fornax Cluster Survey. XI. GC candidates (Jordan+, 2015)J/ApJ/812/34 : UCD candidates in M87/M49/M60 regions (Liu+, 2015)J/A+A/586/A102 : UCDs in the halo of NGC1399 (Voggel+, 2016)J/A+A/608/A142 : Fornax Deep Survey with VST. III. LSB gal. (Venhola+, 2017)J/ApJ/858/102 : Gemini/NIFS and HST obs. of the galaxy M59-UCD3 (Ahn+, 2018)J/A+A/611/A93 : NGC3115 & NGC1399 VEGAS-SSS GCs (Cantiello+, 2018)J/ApJ/862/73 : Deep Chandra obs. of X-ray point sources in M87 (Luan+, 2018)J/ApJS/235/26 : Ultradeep cat. of X-ray point sources in the GC (Zhu+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/876/53https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/876/53http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/876/53https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/876/53https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/876/53http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/876/53GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/876/53/table2 (Catalog of detected X-ray sources in the Fornax cluster)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/876/53/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/876/53/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/876/53/table2?GETtext/xml+votable180.050000true54.07722-35.481060.005555555555555556Cone search capability for table J/ApJ/876/53/table1 (Log of Chandra observations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/876/53/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/876/53/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/876/53/table1?GETtext/xml+votable180.050000true54.8945833-35.43055560.0055555555555555565/8633https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/876/53?format=asciiX-raydefaultJ/ApJ/876/53/table2Catalog of detected X-ray sources in the Fornax clusterSeq[1/1279] Internal index number (1)meta.id;meta.mainintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[54.07/55.21] Source centroid Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-35.9/-35] Source centroid Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainPosErr[0.07/1.87] Position errorarcsecstat.error;posfloatl_S0.5-2The 3{sigma} upper limit flag on S0.5-2meta.code.errorcharS0.5-2[0.1/963.7] The 0.5-2 keV photon flux1e-07ph.cm**-2.s**-1phot.flux;em.X-ray.softfloatE_S0.5-2[0.0/33.1]? Upper 1{sigma} uncertainty in S0.5-21e-07ph.cm**-2.s**-1stat.error;stat.maxfloatnullablee_S0.5-2[0.2/40.7]? Lower 1{sigma} uncertainty in S2-81e-07ph.cm**-2.s**-1stat.errorfloatnullablel_S2-8The 3{sigma} upper limit flag on S2-8meta.code.errorcharS2-8[0.2/361.2] The 2-8 keV photon flux1e-07ph.cm**-2.s**-1phot.flux;em.X-ray.hardfloatE_S2-8[0.0/22.9]? Upper 1{sigma} uncertainty in S2-81e-07ph.cm**-2.s**-1stat.error;stat.maxfloatnullablee_S2-8[0.2/25.8]? Lower 1{sigma} uncertainty in S2-81e-07ph.cm**-2.s**-1stat.errorfloatnullablel_S0.5-8The 3{sigma} upper limit flag on S0.5-8meta.code.errorcharS0.5-8[1.4/1383.4] The 0.5-8 keV photon flux1e-07ph.cm**-2.s**-1phot.flux;em.X-rayfloatE_S0.5-8[0.4/43.6]? Upper 1{sigma} uncertainty in S0.5-81e-07ph.cm**-2.s**-1stat.error;stat.maxfloatnullablee_S0.5-8[0.5/45.6]? Lower 1{sigma} uncertainty in S0.5-81e-07ph.cm**-2.s**-1stat.errorfloatnullablel_F0.5-8The 3{sigma} upper limit flag on F0.5-8meta.code.errorcharF0.5-8[5.1/5036.6] The 0.5-8 keV energy flux in units of 10^-16^erg/s/cm^2^ (2)1e-16mW.m**-2phot.flux;em.X-rayfloatE_F0.5-8[1.6/158.8]? Upper 1{sigma} uncertainty in F0.5-81e-16mW.m**-2stat.error;stat.maxfloatnullablee_F0.5-8[2.0/165.9]? Lower 1{sigma} uncertainty in F0.5-81e-16mW.m**-2stat.errorfloatnullableHR[-0.99/0.94] Hardness ratio (3)phot.flux;arith.ratiofloatE_HR[0.0/0.81] Upper 1{sigma} uncertainty in HRstat.error;stat.maxfloate_HR[0.0/0.81] Lower 1{sigma} uncertainty in HRstat.errorfloatNoteAdditional note flag(s) (4)meta.notecharJ/ApJ/876/53/table1Log of Chandra observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsID[239/17549] Chandra observation identifiermeta.id;obs.param;obsintInstInstrument (ACIS-I or ACIS-S)meta.id;instrcharRAJ2000Aim-point hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Aim-point degree of declination (J2000)pos.eq.dec;meta.mainExp[3.6/98.8] Cleaned exposure timekstime.duration;obs.exposurefloatDateStart date of observation (UT)time.start;obsnullable