- ID:
- ivo://CDS.VizieR/J/ApJ/887/268
- Title:
- Bright QSOs in Southern Hemisphere (QUBRICS)
- Short Name:
- J/ApJ/887/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of absorptions along the lines of sight to bright high-z QSOs is an invaluable cosmological tool that provides a wealth of information on the inter-/circum-galactic medium, dark matter, primordial elements, reionization, fundamental constants, and general relativity. Unfortunately, the number of bright (i<~18) QSOs at z>~2 in the southern hemisphere is much lower than that in the north, due to the lack of wide multiwavelength surveys at decl. {delta}<0{deg}, hampering the effectiveness of observations from southern observatories. In this work we present a new method based on Canonical Correlation Analysis to identify such objects, taking advantage of a number of available databases: Skymapper, Gaia DR2, WISE, and 2MASS. Our QSO candidate sample lists 1476 sources with i<18 over 12400deg^2^ in the southern hemisphere. With a preliminary campaign we observed spectroscopically 69 of them, confirming 54 new bright QSOs at z>2.5, corresponding to a success rate of our method of ~80%. Furthermore, we estimate a completeness of ~90% of our sample at completion of our observation campaign. The new QSOs confirmed by this first and the forthcoming campaigns (QUBRICS survey) will be the targets of subsequent studies using higher resolution spectrographs, like ESPRESSO, UVES, and (in the long term) ELT/HIRES.
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- ID:
- ivo://CDS.VizieR/J/ApJ/871/258
- Title:
- ELQS in SDSS. III. The full ELQS quasar catalog
- Short Name:
- J/ApJ/871/258
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have designed the Extremely Luminous Quasar Survey (ELQS) to provide a highly complete census of unobscured UV-bright quasars during the cosmic noon, z=2.8-5.0. Here we report the discovery of 70 new quasars in the ELQS South Galactic Cap (ELQS-S) quasar sample, doubling the number of known extremely luminous quasars in 4237.3deg^2^ of the Sloan Digital Sky Survey footprint. These observations conclude the ELQS and we present the properties of the full ELQS quasar catalog, containing 407 quasars over 11838.5deg^2^. Our novel ELQS quasar selection strategy resulted in unprecedented completeness at the bright end and allowed us to discover 109 new quasars in total. This marks an increase of ~36% (109/298) in the known population at these redshifts and magnitudes, while we further are able to retain a selection efficiency of ~80%. On the basis of 166 quasars from the full ELQS quasar catalog, which adhere to the uniform criteria of the Two Micron All Sky Survey point source catalog, we measure the bright-end quasar luminosity function (QLF) and extend it one magnitude brighter than previous studies. Assuming a single power law with exponential density evolution for the functional form of the QLF, we retrieve the best-fit parameters from a maximum likelihood analysis. We find a steep bright-end slope of {beta}~-4.1, and we can constrain the bright-end slope to {beta}<=-3.4 with 99% confidence. The density is well modeled by the exponential redshift evolution, resulting in a moderate decrease with redshift ({gamma}~-0.4).
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1219
- Title:
- Galaxy survey in 3 QSO fields
- Short Name:
- J/ApJ/701/1219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an imaging and spectroscopic survey of galaxies in fields around QSOs HE 0226-4110, PKS 0405-123, and PG 1216+069. The fields are selected to have ultraviolet echelle spectra available, which uncover 195 Ly{alpha} absorbers and 13 OVI absorbers along the three sightlines. We obtain robust redshifts for 1104 galaxies of rest-frame absolute magnitude M_R_-5logh<~-16 and at projected physical distances {rho}<~4h^-1^Mpc from the QSOs. Hubble Space Telescope (HST)/WFPC2 images of the fields around PKS 0405-123 and PG 1216+069 are available for studying the optical morphologies of absorbing galaxies. Combining the absorber and galaxy data, we perform a cross-correlation study to understand the physical origin of Ly{alpha} and OVI absorbers and to constrain the properties of extended gas around galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/214/23
- Title:
- IR spectra and photometry of z<0.5 quasars
- Short Name:
- J/ApJS/214/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a step toward a comprehensive overview of the infrared (IR) diagnostics of the central engines and host galaxies of quasars at low redshift, we present Spitzer Space Telescope spectroscopic (5-40{mu}m) and photometric (24, 70, and 160{mu}m) measurements of all Palomar-Green (PG) quasars at z<0.5 and Two Micron All Sky Survey (2MASS) quasars at z<0.3. We supplement these data with Herschel measurements at 160{mu}m. The sample is composed of 87 optically selected PG quasars and 52 near-IR-selected 2MASS quasars. Here we present the data, measure the prominent spectral features, and separate emission due to star formation from that emitted by the dusty circumnuclear torus. We find that the mid-IR (5-30{mu}m) spectral shape for the torus is largely independent of quasar IR luminosity with scatter in the spectral energy distribution (SED) shape of <~0.2dex. Except for the silicate features, no large difference is observed between PG (unobscured --silicate emission) and 2MASS (obscured --silicate absorption) quasars. Only mild silicate features are observed in both cases. When in emission, the peak wavelength of the silicate feature tends to be longer than 9.7{mu}m, possibly indicating effects on grain properties near the active galactic nucleus. The IR color is shown to correlate with the equivalent width of the aromatic features, indicating that the slope of the quasar mid- to far-IR SED is to first order driven by the fraction of radiation from star formation in the IR bands.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/33
- Title:
- Luminous of high-z QSOs with SDSS and WISE. II
- Short Name:
- J/ApJ/829/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper in a series on a new luminous z~5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z~5. Combining our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z~5 quasar sample to date, with 99 quasars in the range of 4.7<=z<5.4 and -29<M_1450_<=-26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/V_a_ method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as {alpha}=-2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope {beta}=-3.58+/-0.24 and a fainter break magnitude M_1450_^*^=-26.98+/-0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a luminosity evolution and density evolution model. Using the best-fit QLF, the contribution of quasars to the ionizing background at z~5 is found to be 18%-45% with a clumping factor C of 2-5. Our sample suggests an evolution of radio loud fraction with optical luminosity but no obvious evolution with redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/37
- Title:
- Luminous WISE-selected quasars in SDSS Stripe 82
- Short Name:
- J/ApJ/861/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopically complete sample of 147 infrared-color-selected active galactic nuclei (AGNs) down to a 22{mu}m flux limit of 20mJy over the ~270deg^2^ of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (Lbol>~10^12^L_{sun}_) and are found out to z~3. We classify the AGNs into three types, finding 57 blue, unobscured Type-1 (broad-lined) sources; 69 obscured, Type-2 (narrow-lined) sources; and 21 moderately reddened Type-1 sources (broad-lined and E(B-V)>0.25). We study a subset of this sample in X-rays and analyze their obscuration to find that our spectroscopic classifications are in broad agreement with low, moderate, and large amounts of absorption for Type-1, red Type-1, and Type-2 AGNs, respectively. We also investigate how their X-ray luminosities correlate with other known bolometric luminosity indicators such as [OIII] line luminosity (L[OIII]) and infrared luminosity (L6{mu}m). While the X-ray correlation with L[OIII] is consistent with previous findings, the most infrared-luminous sources appear to deviate from established relations such that they are either underluminous in X-rays or overluminous in the infrared. Finally, we examine the luminosity function evolution of our sample, and by AGN type, in combination with the complementary, infrared-selected, AGN sample of Lacy et al. (2013), spanning over two orders of magnitude in luminosity. We find that the two obscured populations evolve differently, with reddened Type-1 AGNs dominating the obscured AGN fraction (~30%) for L_5{mu}m_>10^45^erg/s, while the fraction of Type-2 AGNs with L_5{mu}m_<10^45^erg/s rises sharply from 40% to 80% of the overall AGN population.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/11
- Title:
- PS1 z>5.6 quasars follow-up
- Short Name:
- J/ApJS/227/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminous quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far, these studies have been statistically limited by the number of quasars known at these redshifts. Such quasars are rare, and therefore, wide-field surveys are required to identify them, and multiwavelength data are required to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for the z~6 quasars presented in Banados+ (2014AJ....148...14B) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 quasars in the redshift range 5.6<~z<~6.7 that satisfy our selection criteria. Of these quasars, 77 have been discovered with PS1, and 63 of them are newly identified in this paper. We present the composite spectra of the PS1 distant quasar sample. This sample spans a factor of ~20 in luminosity and shows a variety of emission line properties. The number of quasars at z>5.6 presented in this work almost doubles the previously known quasars at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.
- ID:
- ivo://CDS.VizieR/J/AJ/143/119
- Title:
- SDSS Quasar Lens Search. V. Final catalog
- Short Name:
- J/AJ/143/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the final statistical sample of lensed quasars from the Sloan Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined statistical lens sample consists of 26 lensed quasars brighter than i=19.1 and in the redshift range of 0.6<z<2.2 selected from 50826 spectroscopically confirmed quasars in the SDSS Data Release 7 (DR7), where we restrict the image separation range to 1"<{theta}<20" and the i-band magnitude differences in two images to be smaller than 1.25mag. The SDSS-DR7 quasar catalog also contains 36 additional lenses identified with various techniques. In addition to these lensed quasars, we have identified 81 pairs of quasars from follow-up spectroscopy, 26 of which are physically associated binary quasars. The statistical lens sample covers a wide range of image separations, redshifts, and magnitudes, and therefore is suitable for systematic studies of cosmological parameters and surveys of the structure and evolution of galaxies and quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/38
- Title:
- SDSS RM Project: CIV lags & LCs from 4yrs of data
- Short Name:
- J/ApJ/887/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present reverberation-mapping (RM) lags and black hole mass measurements using the CIV{lambda}1549 broad emission line from a sample of 348 quasars monitored as a part of the Sloan Digital Sky Survey RM Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days, allowing us to measure lags up to ~750days in the observed frame (this corresponds to a rest-frame lag of ~300days in a quasar at z=1.5 and ~190days at z=3). We report significant time delays between the continuum and the CIV{lambda}1549 emission line in 48 quasars, with an estimated false-positive detection rate of 10%. Our analysis of marginal lag measurements indicates that there are on the order of ~100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black hole masses and fit an updated CIV radius-luminosity relationship. Our results significantly increase the sample of quasars with CIV RM results, with the quasars spanning two orders of magnitude in luminosity toward the high-luminosity end of the CIV radius-luminosity relation. In addition, these quasars are located at some of the highest redshifts (z~1.4-2.8) of quasars with black hole masses measured with RM.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/26
- Title:
- Spectroscopic follow-up of the QUBRICS quasars
- Short Name:
- J/ApJS/250/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the spectroscopic follow-up of the QUasars as BRIght beacons for Cosmology in the Southern Hemisphere (QUBRICS; Calderone+ 2019, J/ApJ/887/268) survey. The selection method is based on a machine-learning approach applied to photometric catalogs, covering an area of ~12400deg^2^ in the Southern Hemisphere. The spectroscopic observations started in 2018 and identified 55 new, high-redshift (z>=2.5), bright (i<=18) quasi-stellar objects (QSOs), with the catalog published in late 2019. Here we report the current status of the survey, bringing the total number of bright QSOs at z>=2.5 identified by QUBRICS to 224. The success rate of the QUBRICS selection method, in its most recent training, is estimated to be 68%. The predominant contaminant turns out to be lower-z QSOs at z<2.5. This survey provides a unique sample of bright QSOs at high z available for a number of cosmological investigations. In particular, carrying out the redshift drift measurements (Sandage Test) in the Southern Hemisphere, using the High Resolution Spectrograph at the 39m Extremely Large Telescope appears to be possible with less than 2500hr of observations spread over 30 targets in 25yr.