Person: Tananbaum, Harvey
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Tananbaum
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Tananbaum, Harvey
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Publication A Full Year's Chandra Exposure on Sloan Digital Sky Survey Quasars From the Chandra Multiwavelength Project(IOP Publishing, 2008) Green, Paul J.; Aldcroft, Thomas; Richards, G. T.; Barkhouse, W. A.; Constantin, Ana-Maria; Haggard, D.; Karovska, Margarita; Kim, D.-W.; Kim, M.; Viklinin, Alexey; Anderson, S. F.; Mossman, Amy; Kashyap, Vinay; Myers, A. C.; Silverman, J. D.; Wilkes, Belinda; Tananbaum, HarveyWe study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2 3, substantially expanding the known sample. We find no evidence for evolution out to z ∼ 5 for either the X-ray photon index Γ or for the ratio of optical/UV to X-ray flux αox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022 cm−2, but the fraction might reach ∼1/3 if most nondetections are absorbed. We confirm a significant correlation between αox and optical luminosity, but it flattens or disappears for fainter (MB −23) active galactic nucleus (AGN) alone. We report significant hardening of Γ both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, we find no evidence for unusual distributions of either αox or Γ.Publication The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1.(IOP Publishing, 1994) Wilkes, Belinda; Tananbaum, Harvey; Worrall, Diana; Avni, Yoram; Oey, M. S.; Flanagan, JoanWe present the first volume of the Einstein quasar database. The database includes estimates of the X-ray count rates, fluxes, and luminosities for 514 quasars and Seyfert 1 galaxies observed with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. All were previously known optically selected or radio-selected objects, and most were the targets of the X-ray observations. The X-ray properties of the Active Galactic Nuclei (AGNs) have been derived by reanalyzing the IPC data in a systematic manner to provide a uniform database for general use by the astronomical community. We use the database to extend earlier quasar luminosity studies which were made using only a subset of the currently available data. The database can be accessed on internet via the SAO Einstein on-line system ('Einline') and is available in ASCII format on magnetic tape and DOS diskette.Publication PKS 0483-436 - A high-redshift quasar with strong X-ray absorption(IOP Publishing, 1992) Wilkes, Belinda; Elvis, Martin; Fiore, Fabrizio; McDowell, Jonathan; Tananbaum, Harvey; Lawrence, AndrewThe first X-ray spectrum of a high-redshift (z = 2.85) quasar is reported. The Rosat PSPC spectrum of PKS 0438-436, covering 0.3-9 keV in the quasar's rest frame, reveals unexpected absorption of about 1 x 10 exp 22/sq cm, assuming it occurs at the source. Only one other high-luminosity quasar (of greater than about 50 observed by Einstein) shows significant absorption in its X-ray spectrum. Of the common line-of-sight absorbers, only highly ionized Ly-alpha forest clouds may be able to explain this amount of absorption. Candidates for an intrinsic absorber are discussed. Absorption at about 1 keV (rest frame) is due primarily to heavy elements. (O, Ne, Mg, Si, S) raising the possibility of measuring early universe abundances via X-ray absorption in this and like quasars. PKS 0438-436 may be a high-redshift member of a population of quasars which can contribute to the X-ray background above 2 keV, without being detectable by previous imaging missions.Publication The Luminosity Function of X‐Ray–selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift(IOP Publishing, 2008) Silverman, J. D.; Green, P. J.; Barkhouse, W. A.; Kim, Dong-Woo; Kim, M.; Wilkes, Belinda; Cameron, R. A.; Hasinger, G.; Jannuzi, B. T.; Smith, M. G.; Smith, P. S.; Tananbaum, HarveyWe present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of AGNs up to z ~ 5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (LX > 1044 ergs s−1) AGNs. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower LX range of the XLF. Our sample is selected from both the hard (z < 3, f2–8 keV > 6.3 × 10−16 ergs cm −2 s−1) and soft (z > 3, f0.5–2.0 keV > 1.0 × 10−16 ergs cm −2 s−1) energy band detections. Within our optical magnitude limits (r', i' < 24), we achieve an adequate level of completeness (>50%) regarding X-ray source identification (i.e., redshift). We find that the luminosity function is similar to that found in previous X-ray surveys up to z ~ 3 with an evolution dependent on both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGNs with an evolution rate similar to that found by studies of optically selected QSOs. Based on our XLF, we assess the resolved fraction of the cosmic X-ray background, the cumulative mass density of SMBHs, and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z ~ 2 is plausible, although at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high-redshift AGNs at z gsim 3, which is achievable with the upcoming Chandra surveys.Publication Chandra Multiwavelength Project X‐Ray Point Source Catalog(IOP Publishing, 2007) Kim, Minsun; Kim, Dong‐Woo; Wilkes, Belinda; Green, Paul J.; Kim, Eunhyeuk; Anderson, Craig; Barkhouse, Wayne A.; Evans, Nancy; Ivezi?, ?eljko; Karovska, Margarita; Kashyap, Vinay L.; Lee, Myung Gyoon; Maksym, Peter; Mossman, Amy; Silverman, John D.; Tananbaum, HarveyWe present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with ~6800 X-ray sources detected in 149 Chandra observations covering ~10 deg2. The full ChaMP catalog sample is 7 times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124 ks, corresponding to a deepest X-ray flux limit of f0.5-8.0 = 9 × 10-16 ergs cm-2 s-1. The ChaMP X-ray data have been uniformly reduced and analyzed with ChaMP-specific pipelines and then carefully validated by visual inspection. The ChaMP catalog includes X-ray photometric data in eight different energy bands as well as X-ray spectral hardness ratios and colors. To best utilize the ChaMP catalog, we also present the source reliability, detection probability, and positional uncertainty. To quantitatively assess those parameters, we performed extensive simulations. In particular, we present a set of empirical equations: the flux limit as a function of effective exposure time and the positional uncertainty as a function of source counts and off-axis angle. The false source detection rate is ~1% of all detected ChaMP sources, while the detection probability is better than ~95% for sources with counts gsim30 and off-axis angle <5'. The typical positional offset between ChaMP X-ray source and their SDSS optical counterparts is 0.7'' ± 0.4'', derived from ~900 matched sources.Publication Chandra Multiwavelength Project X‐Ray Point Source Number Counts and the Cosmic X‐Ray Background(IOP Publishing, 2007) Kim, Minsun; Wilkes, Belinda; Kim, Dong‐Woo; Green, Paul; Barkhouse, Wayne A.; Lee, Myung Gyoon; Silverman, John D.; Tananbaum, HarveyWe present the Chandra Multiwavelength Project (ChaMP) X-ray point source number counts and cosmic X-ray background (CXRB) flux densities in multiple energy bands. From the ChaMP X-ray point source catalog, ~5500 sources are selected, covering 9.6 deg2 in sky area. To quantitatively characterize the sensitivity and completeness of the ChaMP sample, we perform extensive simulations. We also include the ChaMP+CDFs (Chandra Deep Fields) number counts to cover large flux ranges from 2 × 10-17 to 2.4 × 10-12 (0.5-2 keV) and from 2 × 10-16 to 7.1 × 10-12 (2-8 keV) ergs cm-2 s-1. The ChaMP and the ChaMP+CDFs differential number counts are well fitted with a broken power law. The best-fit faint and bright power indices are 1.49 ± 0.02 and 2.36 ± 0.05 (0.5-2 keV), and 1.58 ± 0.01 and 2.59img1.gif (2-8 keV), respectively. We detect breaks in the differential number counts that appear at different fluxes in different energy bands. Assuming a single power-law model for a source spectrum, we find that the same population(s) of soft X-ray sources causes the break in the differential number counts for all energy bands. We measure the resolved CXRB flux densities from the ChaMP and the ChaMP+CDFs number counts with and without bright target sources. By adding the known unresolved CXRB to the ChaMP+CDF resolved CXRB, we also estimate total CXRB flux densities. The fractions of the resolved CXRB without target sources are 78% ± 1% and 81% ± 2% in the 0.5-2 and 2-8 keV bands, respectively, somewhat lower than but generally consistent with earlier numbers because of their large errors. These fractions increase by ~1% when target sources are included.Publication Chandra Multiwavelength Project: Normal Galaxies at Intermediate Redshift(IOP Publishing, 2006) Kim, D.‐W.; Barkhouse, W. A.; Romero‐Colmenero, E.; Green, P. J.; Kim, M.; Mossman, Amy; Schlegel, E.; Silverman, J. D.; Aldcroft, Thomas; Anderson, C.; Ivezic, Z.; Kashyap, V.; Tananbaum, Harvey; Wilkes, BelindaWe have investigated 136 Chandra extragalactic sources, including 93 galaxies with narrow emission lines (NELGs) and 43 with only absorption lines (ALGs). Based on fX/fO, LX, X-ray spectral hardness, and optical emission-line diagnostics, we have conservatively classified 36 normal galaxies and 71 AGNs. Their redshift ranges from 0.01 to 1.2, with normal galaxies in the range z = 0.01-0.3. Our normal galaxies appear to share characteristics with local galaxies, as expected from the X-ray binary populations and the hot interstellar matter (ISM). In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in LX/LB, within the limited z range (lesssim0.1). The best-fit slope of our log(N)-log(S) relationship is -1.5 for both S (0.5-2 keV) and B (0.5-8 keV) energy bands, which is considerably steeper than that of the AGN-dominated cosmic background sources, but slightly flatter than the previous estimate, indicating that normal galaxies will not exceed the AGN population until fX(0.5-2.0 keV) ~ 2 × 10-18 ergs s-1 cm-2 (a factor of ~5 lower than the previous estimate). A group of NELGs appear to be heavily obscured in X-rays. After correcting for intrinsic absorption, their X-ray luminosities could be LX > 1044 ergs s-1, making them type 2 quasar candidates. While most X-ray-luminous ALGs do not appear to be significantly absorbed, we found two heavily obscured objects that could be as luminous as an unobscured broad-line quasar. Among 43 ALGs, we found two E+A galaxy candidates. The X-ray spectra of both galaxies are soft, and one of them has a nearby close companion galaxy, supporting the merger/interaction scenario rather than the dusty starburst hypothesis.Publication The diversity of soft X-ray spectra in quasars(IOP Publishing, 1985) Elvis, Martin; Wilkes, Belinda; Tananbaum, HarveySoft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for the quasar NAB 0205 + 024, 0.6 +0.3 or -0.2 for the quasar B2 1028 + 313, and 2.2 + or -0.4 for the quasar PG 1211 + 143. None of the quasars shows any evidence for a column density of cold matter in excess of the galactic values. The derived spectra demonstrate that there is no single universal power law slope for quasar X-ray spectra. The implications of these results for the X-ray background, X-ray continuum emission mechanisms, and the production of the optical/UV emission lines are briefly discussed.Publication Chandra Multiwavelength Project. I. First X‐Ray Source Catalog(IOP Publishing, 2004) Kim, D.‐W.; Cameron, R. A.; Drake, Jeremy; Evans, Nancy; Freeman, P.; Gaetz, Terrance; Ghosh, H.; Green, P. J.; Harnden, F. R. Jr.; Karovska, Margarita; Kashyap, Vinay; Maksym, Peter; Ratzlaff, Peter; Schlegel, E. M.; Silverman, J. D.; Tananbaum, Harvey; Viklinin, Alexey; Wilkes, Belinda; Grimes, J. P.The Chandra Multiwavelength Project (ChaMP) is a wide-area (~14 deg2) survey of serendipitous Chandra X-ray sources, aiming to establish fair statistical samples covering a wide range of characteristics (such as absorbed active galactic nuclei, high-z clusters of galaxies) at flux levels (fX ~ 10-15 to 10-14 ergs s-1 cm-2) intermediate between the Chandra deep surveys and previous missions. We present the first ChaMP catalog, which consists of 991 near on-axis, bright X-ray sources obtained from the initial sample of 62 observations. The data have been uniformly reduced and analyzed with techniques specifically developed for the ChaMP and then validated by visual examination. To assess source reliability and positional uncertainty, we perform a series of simulations and also use Chandra data to complement the simulation study. The false source detection rate is found to be as good as or better than expected for a given limiting threshold. On the other hand, the chance of missing a real source is rather complex, depending on the source counts, off-axis distance (or PSF), and background rate. The positional error (95% confidence level) is usually less than 1'' for a bright source, regardless of its off-axis distance, while it can be as large as 4'' for a weak source (~20 counts) at a large off-axis distance (Doff-axis > 8'). We have also developed new methods to find spatially extended or temporary variable sources, and those sources are listed in the catalog.Publication The Chandra Multiwavelength Project: Optical Follow‐up of Serendipitous Chandra Sources(IOP Publishing, 2004) Green, P. J.; Silverman, J. D.; Cameron, R. A.; Kim, D.‐W.; Wilkes, Belinda; Barkhouse, W. A.; LaCluyze, A.; Morris, D.; Mossman, Amy; Ghosh, H.; Grimes, J. P.; Jannuzi, B. T.; Tananbaum, Harvey; Aldcroft, Thomas; Baldwin, J. A.; Chaffee, F. H.; Dey, A.; Dosaj, A.; Evans, Nancy; Fan, X.; Foltz, C.; Gaetz, Terrance; Hooper, E. J.; Kashyap, Vinay; Mathur, S.; McGarry, M. B.; Romero‐Colmenero, E.; Smith, M. G.; Smith, P. S.; Smith, R. C.; Torres, Guillermo; Viklinin, Alexey; Wik, D. R.We present follow-up optical g', r', and i' imaging and spectroscopy of serendipitous X-ray sources detected in six archival Chandra images included in the Chandra Multiwavelength Project (ChaMP). Of the 486 X-ray sources detected between 3 × 10-16 and 2 × 10-13 (with a median flux of 3 × 10-15) ergs cm-2 s-1, we find optical counterparts for 377 (78%), or 335 (68%) counting only unique counterparts. We present spectroscopic classifications for 125 objects, representing 75% of sources with r* < 21 optical counterparts (63% to r* = 22). Of all classified objects, 63 (50%) are broad-line active galactic nuclei (AGNs), which tend to be blue in (g*-r*) colors. X-ray information efficiently segregates these quasars from stars, which otherwise strongly overlap in these SDSS colors until z > 3.5. We identify 28 sources (22%) as galaxies that show narrow emission lines, while 22 (18%) are absorption line galaxies. Eight galaxies lacking broad-line emission have X-ray luminosities that require they host an AGN (logLX > 43). Half of these have hard X-ray emission suggesting that high gas columns obscure both the X-ray continuum and the broad emission line regions. We find objects in our sample that show signs of X-ray or optical absorption, or both, but with no strong evidence that these properties are coupled. ChaMP's deep X-ray and optical imaging enable multiband selection of small and/or high-redshift groups and clusters. In these six fields we have discovered three new clusters of galaxies, two with z > 0.4, and one with photometric evidence for a similar redshift.