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NASA NTRS2013

GBT Detection of Polarization-Dependent HI Absorption and HI Outflows in Local ULIRGs and Quasars

We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST) sample of ultraluminous infrared galaxies (ULIRGs; L(sub 8 - 1000 micron) > 10(exp 12) solar L) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGN) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of HI absorption (emission) to be 100% (29%) in ULIRGs with HI detections, 100% (88%) in FIR-strong quasars, and 63% (100%) in FIR-weak quasars. The absorption features are associated with powerful neutral outflows that change from being mainly driven by star formation in ULIRGs to being driven by the AGN in the quasars. These outflows have velocities that exceed 1500 km/s in some cases. Unexpectedly, we find polarization-dependent HI absorption in 57% of our spectra (88% and 63% of the FIR-strong and FIR-weak quasars, respectively). We attribute this result to absorption of polarized continuum emission from these sources by foreground HI clouds. About 60% of the quasars displaying polarized spectra are radio-loud, far higher than the approx 10% observed in the general AGN population. This discrepancy suggests that radio jets play an important role in shaping the environments in these galaxies. These systems may represent a transition phase in the evolution of gas-rich mergers into "mature" radio galaxies.

Teng, Stacy H.↗
NASA NTRS2017

Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745*

SDSS J2222+2745 is a galaxy cluster at z = 0.49, strongly lensing a quasar at z = 2.805 into six widely separated images. In recent Hubble Space Telescope imaging of the field, we identify additional multiply lensed galaxies and confirm the sixth quasar image that was identified by Dahle et al. We used the Gemini-North telescope to measure a spectroscopic redshift of z = 4.56 of one of the lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a lensed galaxy at z = 2.3. This galaxy also appears in absorption in our Gemini spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is in agreement with the recent time delay measurements of Dahle et al., who found T(sub AB) = 47.7 +/- 6.0 days and T(sub AC) = 722 +/- 24 days. We use the observed time delays to further constrain the model, and find that the model-predicted time delays of the three faint images of the quasar are T(sub AD) = 502+/- 68 days, T( sub AE) = 611 +/- 75 days, and T(sub AF) = 415 +/- 72 days. We have initiated a follow-up campaign to measure these time delays with Gemini North. Finally, we present initial results from an X-ray monitoring program with Swift, indicating the presence of hard X-ray emission from the lensed quasar, as well as extended X-ray emission from the cluster itself, which is consistent with the lensing mass measurement and the cluster velocity dispersion.

Sharon, Keren↗
NASA NTRS2016

Evidence for the Thermal Sunyaev Zeldovich Effect Associated with Quasar Feedback

Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalogue, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We constrain the form of the far-infrared emission and find 3 sigma-4 sigma evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy (6.2 plus or minus 1.7) × 10 (exp 60) erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of (1-5) × 10(exp 12) h(exp −1) solar mass that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. Our measurements are consistent with quasars depositing up to (14.5 +/- 3.3)tau (sub 8)(exp -1) per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is tau(sub 8) x 108 yr. For high quasar host masses, approximately 10(exp 13) h(exp −1) solar mass, this percentage will be reduced. Furthermore, the uncertainty on this percentage is only statistical and additional systematic uncertainties enter at the 40 per cent level. The SEDs are dust dominated in all bands and we consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 3 sigma-4 sigma level for most models.

Sunyaev-Zeldovich (SZ)↗
NASA NTRS1980

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

Grindlay, J. E.↗
NASA NTRS1980

X-ray properties of quasars

The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.

Ku, W. H.-M.↗
NASA NTRS1981

One millimeter continuum observations of high redshift quasars

Upper limits to the one-millimeter continuum flux densities of the high redshift quasars B2 1225 + 31, Ton 490, and PHL 957 are presented. The upper limit to the power observed from these quasars at 1 mm is, on the average, one half of the observed power in the continuum at L-alpha. These observations are used to constrain the temperature of a hypothetical dust shell which reddens the quasar line and continuum emission by an extinction optical depth sufficient to account for the anomalously low L-alpha/H-alpha emission line ratio observed in each of these quasars. For the quasars studied, dust shell temperatures between 25 K and 50 to 95 K are prohibited by the present data. A dust shell at a temperature within this span reradiating all the power absorbed from the quasar ultraviolet continuum would produce a one-millimeter flux density greater than the measured upper limit. The average radius of the model dust shell cannot be between 70 kpc and 1 Mpc.

Ennis, D. J.↗
NASA NTRS1982

Discovery of a narrow line quasar

A stellar object is reported which, while having X-ray and optical luminosities typical of quasars, has narrow permitted and forbidden emission lines over the observed spectral range. The narrow-line spectrum is high-excitation, the Balmer lines seem to be recombinational, and a redder optical spectrum than that of most quasars is exhibited, despite detection as a weak radio source. The object does not conform to the relationships between H-beta parameters and X-ray flux previously claimed for a large sample of the active galactic nuclei. Because reddish quasars with narrow lines, such as the object identified, may not be found by the standard techniques for the discovery of quasars, the object may be a prototype of a new class of quasars analogous to high-luminosity Seyfert type 2 galaxies. It is suggested that these objects cannot comprise more than 10% of all quasars.

Stocke, J.↗
NASA NTRS1981

Summary of the workshop on active galaxies and quasars

The paper reports highlights of discussions carried out at the Tenth Texas Symposium on Relativistic Astrophysics concerning BL Lacertae objects and quasars and their relationship to active galactic nuclei. The discussions considered X-ray, optical and radio observations of active galaxies and quasars showing features which may be interpreted as jets or beams, and X-ray and VLBI observations of core-jet structures exhibiting apparent supraluminal expansion. Attention was also given to the properties of the energy source in the center of the active galaxies and quasars, the nature of quasar emission line regions, the production of the continuum in quasars and active galactic nuclei, and evidence for the association of quasars and BL Lac objects with galaxies.

Weistrop, D.↗
NASA NTRS1983

Optical and X-ray observations of faint quasars in an optically selected sample

The confirmation of six quasars from spectrographic observations made in 1981 using the Multiple Mirror Telescope, and the characterization of 10 quasars from 1980 Einstein-Observatory X-ray observations (using both imaging proportional counter and high-resolution imager), are reported. The candidates had been selected by Formiggini et al. (1980) in a 1.72-sq-deg region centered on 13h 6 deg, on the basis of ultraviolet excess and a limiting B magnitude of 19.20. A total sample of 10 UV-excess quasars of this magnitude has now been confirmed, for an integral surface density of 5.8 + or - 1.8 per sq deg. Confirmation of three objects from another sample with B less than 18.25 as quasars yielded a surface density of 0./59 + or - 0.13 per sq deg at that magnitude. Data from the complete samples were used to compute the number-flux relation, found to be described by a power law with a 2.25 index for quasars with B between 17.0 and 19.2. From the X-ray observations it was determined that quasars with z less than 2.2 and B less than 19.20 contribute about 15 percent to the cosmic 2-keV background.

Marshall, H. L.↗
NASA NTRS1984

A complete sample of quasars at B = 19.80

A quasar candidate spectroscopic UV-excess survey with B less than 19.80 has yielded 35 quasars in the 1.75 sq deg region studied. The X-ray data for the 35 quasars are used to show that quasars with B lower than 19.80 and z lower than 2.2 constitute 24 + 10, -8 percent of the observed X-ray background at 2 keV. This sample is combined with one containing 22 quasars with B values lower than 18.25, and it is noted that fits of evolution and luminosity functions are substantially similar to previous results, although the confidence limits for the model parameters are reduced by a factor of 2. Pure luminosity evolution models are found to produce very good fits to the observed N(less than B) data, and are used to estimate the overall contribution of quasars to the X-ray background.

Marshall, H. L.↗
NASA NTRS1984

A search for quasars in the Virgo cluster region

Using objective-prism plates taken with the 44-arcmin objective prism mounted on the UK Schmidt telescope, 53 emission-line quasar candidates and 29 ultraviolet-excess objects (possible low-redshift quasars) have been found in a 5 x 5-degree field centered on 12 h 27 m, + 13 deg 30 min (1950) in the Virgo cluster of galaxies. Eighteen of these 82 candidates were observed using the double spectrograph on the Palomar 5-meter telescope; 13 of the observed objects proved to be quasars. The broad-absorption-line QSO Q1232 + 134 is the first example of the class to show broad low-ionization absorption lines (such as Mg II 2798 A) in addition to the usual high-excitation lines such as Nv 1240 A. Although no conclusive evidence for quasar-galaxy associations is found in this field, there do exist nonuniformities in the distribution of the quasar candidates which may merit further investigation. These objects will provide a useful network of probes for absorbing material in the Virgo cluster. The lines-of-sight to two of the confirmed quasars pass very close to NGC galaxies; the respective projected QSO-galaxy separations are only 4 and 11 kpc at the assumed distance of the Virgo cluster.

He, X.-T.↗
NASA NTRS1985

The quasars 1038 + 528 A and B

The results of VLBI observations of the quasars 1038 + 528 A and B at 2.8, 3.6, 13, and 18 cm at various times between November 1979 and March 1981 are reported. The observations and data calibration are described, as are the mapping and astrometric techniques applied in the study. Both quasars are found to have 'core-jet' morphologies. The core of the A quasar dominates its morphology at centrimetric wavelengths with the brightness temperature of its 400 pc long jet being about 1/100 that of the core. By contrast, the 'jet' in the B quasar is very short (about 70 pc); the tail of this jet has the steepest spectral index found to date in extragalactic compact sources, indicating that high electron losses are responsible for the shortness of the jet. No evidence for appreciable morphological change in the B quasar was found over the time span of the study, whereas a new feature may be emerging from the A quasar core at superluminal speed.

Marcaide, J. M.↗
NASA NTRS1985

The diversity of soft X-ray spectra in quasars

Soft 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.

Elvis, M.↗
NASA NTRS1986

X-ray spectra of PG quasars. I - The continuum from X-rays to infrared

Einstein IPC X-ray spectra for a sample of eight optically selected quasars from the Palomar Bright Quasar survey are presented. The quasars have a mean power law energy slope which in five individual cases is inconsistent with the value found in hard X-ray selection criterion rather than luminosity, redshift, or U-B color. New IUE and optical continuum spectra and infrared photometry are presented for these quasars. The data are combined into log vf(v) and log v distributions which support the decomposition of the overall quasar spectrum into a power law plus a superposed optical-UV 'big bump' which may be due to an accretion disk. At least six of the quasars have vf(v)s which are roughly constant between their infrared and X-ray power laws, suggesting a strong link between the two regions.

Elvis, Martin↗
NASA NTRS1991

An ultraviolet atlas of quasar and blazar spectra

An atlas is presented which provides a uniformly extracted and calibrated set of over 1000 UV spectra of the highest possible SNR for quasars and blazars observed with the IUE. The spectra show that quasars and blazars vary more in the UV than in the optical, and show increasing variability toward shorter wavelengths. The low-redshift quasars have Ly-alpha emission lines dominated by strong, narrow components, while high-redshift quasars seem to lack such narrow components. Absorption by gas in the Galaxy is ubiquitous in strong interstellar lines of C II, O I, Si II, Mg II, and Fe II. Of special note is the detection of Fe II and Mg II absorption due to gas associated with NGC3067 in the quasar 3C 232. Over 20 percent of the combined quasar and Seyfert 1 sample show either associated absorption or absorption just shortward of the emission redshift.

Kinney, A. L.↗
NASA NTRS1991

An astrophysics data program investigation of a synoptic study of quasar continua

A summary of the program is presented. The major product of the program, an atlas of quasar energy distributions, is presented in the appendices along with papers written as a result of this research. The topics covered in the papers include: (1) accurate galactic N(sub h) values toward quasars and active galactic nuclei (AGN); (2) weak bump quasars; (3) millimeter measurements of hard x ray selected active galaxies- implications for the nature of the continuous spectrum; (3) persistence and change in the soft x ray spectrum of the quasar PG1211+143; (4) the soft x ray excess in einstein quasar spectra; and (5) EXOSAT x ray spectra of quasars.

Elvis, Martin↗
NASA NTRS1993

The Hubble Space Telescope Snapshot Survey. IV - A summary of the search for gravitationally lensed quasars

We report the concluding results of the HST Snapshot Survey for gravitationally lensed quasars. New observations of 153 high-luminosity z above 1 quasars are presented, bringing to 498 the total number of quasars observed in the survey. The new observations do not reveal new candidates for gravitational lensing. We present tables summarizing all of the snapshot observations, with measured V-magnitudes, accurate to 0.1 mag, for each of the quasars successfully observed. The observed frequency of lensing of quasars into multiple images is 3-6 out of 502, depending on whether one counts candidates that are not yet securely confirmed and cases in which clusters play a role. This frequency is in the range predicted by calculations with a vanishing cosmological constant, assuming galaxies can be modeled by unevolving isothermal spheres dominated in their centers by dark matter. The observed frequency is an order of magnitude lower than expected in such models when the universe is strongly dominated by a cosmological constant. This conclusion is, however, sensitive to the model assumptions and to the precise number of actual lensed quasars.

Maoz, D.↗
NASA NTRS1994

The second serendipitous discovery of a z greater than 4 quasar

This paper describes the chance discovery of the z = 4.210 quasar PC 0027+0521. The quasar was found during a grism survey for emission line objects. The Lyman alpha line luminosity and the redshift of the quasar satisfy the survey selection criteria, but the grism spectrum of the quasar was heavily contaminated by the spectra of three nearby objects. The quasar was discovered only because it happened to lie in the slit of a spectroscopic observation of a nearby emission line candidate. The quasar is the faintest z greater than 4 object yet found, and has strong narrow emission lines.

Schneider, Donald P.↗