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91. Blazars in unidentified {gamma}-ray sources
ID:
ivo://CDS.VizieR/J/ApJ/752/61
Title:
Blazars in unidentified {gamma}-ray sources
Short Name:
J/ApJ/752/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.
92. Blazar (sub-)mm & {gamma}-ray luminosities
ID:
ivo://CDS.VizieR/J/ApJ/754/23
Title:
Blazar (sub-)mm & {gamma}-ray luminosities
Short Name:
J/ApJ/754/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The coexistence of Planck and Fermi satellites in orbit has enabled the exploration of the connection between the (sub-)millimeter and {gamma}-ray emission in a large sample of blazars. We find that the {gamma}-ray emission and the (sub-)mm luminosities are correlated over five orders of magnitude, L_{gamma}_{prop.to}L_(sub-)mm_. However, this correlation is not significant at some frequency bands when simultaneous observations are considered. The most significant statistical correlations, on the other hand, arise when observations are quasi-simultaneous within two months. Moreover, we find that sources with an approximate spectral turnover in the middle of the mm-wave regime are more likely to be strong {gamma}-ray emitters. These results suggest a physical relation between the newly injected plasma components in the jet and the high levels of {gamma}-ray emission.
93. Blazars with {gamma}-ray counterparts. I.
ID:
ivo://CDS.VizieR/J/ApJS/206/12
Title:
Blazars with {gamma}-ray counterparts. I.
Short Name:
J/ApJS/206/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new method for identifying blazar candidates by examining the locus, i.e., the region occupied by the Fermi {gamma}-ray blazars in the three-dimensional color space defined by the WISE infrared colors. This method is a refinement of our previous approach that made use of the two-dimensional projection of the distribution of WISE {gamma}-ray-emitting blazars (the Strip) in the three WISE color-color planes. In this paper, we define the three-dimensional locus by means of a principal component analysis of the color distribution of a large sample of blazars composed of all the ROMA-BZCAT sources with counterparts in the WISE All-Sky Catalog associated with {gamma}-ray sources in the second Fermi-LAT catalog (2FGL; the WISE Fermi blazars sample, WFB). Our new procedure yields a total completeness of c_tot_~81% and a total efficiency of e_tot_~97%. We also obtain local estimates of the efficiency and completeness as functions of the WISE colors and galactic coordinates of the candidate blazars. The catalog of all WISE candidate blazars associated with the WFB sample is also presented, complemented by archival multi-frequency information for the alternative associations. Finally, we apply the new association procedure to all {gamma}-ray blazars in the 2FGL and provide a catalog containing all the {gamma}-ray candidate blazars selected according to our procedure.
94. Blazars with {gamma}-ray counterparts. II.
ID:
ivo://CDS.VizieR/J/ApJS/206/13
Title:
Blazars with {gamma}-ray counterparts. II.
Short Name:
J/ApJS/206/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
A significant fraction (~30%) of the high-energy gamma-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) are still of unknown origin, being not yet associated with counterparts at low energies. We recently developed a new association method to identify if there is a {gamma}-ray blazar candidate within the positional uncertainty region of a generic 2FGL source. This method is entirely based on the discovery that blazars have distinct infrared colors with respect to other extragalactic sources found, thanks to the Wide-field Infrared Survey Explorer (WISE) all-sky observations. Several improvements have also been performed to increase the efficiency of our method in recognizing {gamma}-ray blazar candidates. In this paper we applied our method to two different samples, the first constituted by unidentified {gamma}-ray sources (UGSs), and the second by active galaxies of uncertain type, both listed in the 2FGL. We present a catalog of IR counterparts for ~20% of the UGSs investigated. Then, we also compare our results for the associated sources with those present in the literature. In addition, we illustrate the extensive archival research carried out to identify the radio, infrared, optical, and X-ray counterparts of the WISE-selected, {gamma}-ray blazar candidates. Finally, we discuss the future developments of our method based on ground-based follow-up observations.
95. B light curve of 1WGA J0447.9-0322
ID:
ivo://CDS.VizieR/J/AJ/133/965
Title:
B light curve of 1WGA J0447.9-0322
Short Name:
J/AJ/133/965
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the historic light curve of 1WGA J0447.9-0322, spanning the time interval from 1962 to 1991, built using the Asiago archive plates. The source shows small fluctuations of about 0.3mag around B=16 until 1986 and a fast dimming of its average level by about 0.5mag after that date, again with small short-term variations. The variability pattern is within the values shown by other QSOs with long-term monitoring, notwithstanding its high X-ray/optical ratio. We also present its overall spectral energy distribution using literature data and recent UV-optical Swift observations.
96. BOSS narrow CIV absorption lines. III.
ID:
ivo://CDS.VizieR/J/MNRAS/462/2980
Title:
BOSS narrow CIV absorption lines. III.
Short Name:
J/MNRAS/462/2980
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we extend our work of IV {lambda}{lambda}1548,1551 narrow absorption lines (NALs) with z_abs_<<z_em_ on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS) to collect CIV NALs with z_abs_<=z_em_ from blue to red wings of CIV {lambda}1549 emission lines. Together with IV NALs with 1.4544<=z_abs_<=4.9224 in surveyed spectral region redward of Ly{alpha} until red wing of CIV {lambda}1549 emission line. We find that the stronger CIV NALs tend to be the more saturated absorptions, and associated systems (z_abs_~=z_em_) seem to have larger absorption strengths when compared to intervening ones (z_abs_<<z_em_). The redshift density evolution behaviour of absorbers (the number of absorbers per redshift path) is similar to the history of the cosmic star formation. When compared to the quasar-frame velocity ({beta}) distribution of MgII absorbers, the {beta} distribution of CIV absorbers is broader at {beta}~=0, shows longer extended tail, and exhibits a larger dispersion for environmental absorptions. In addition, for associated CIV absorbers, we find that low-luminosity quasars seem to exhibit smaller {beta} and stronger absorptions when compared to high-luminosity quasars.
97. BOSS narrow CIV absorption lines. II. zem>2.4
ID:
ivo://CDS.VizieR/J/ApJS/215/12
Title:
BOSS narrow CIV absorption lines. II. zem>2.4
Short Name:
J/ApJS/215/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
As the second work in a series of papers aiming to detect absorption systems in the quasar spectra of the Baryon Oscillation Spectroscopic Survey, we continue the analysis of Paper I (Chen+, 2014, J/ApJS/210/7; 2014ApJS..212...17C) by expanding the quasar sample to those quasars with z_em_>2.4. This yields a sample of 21963 appropriate quasars to search for narrow CIV{lambda}{lambda}1548,1551 absorptions with W_r_>=0.2{AA} for both lines. There are 9708 quasars with at least one appropriate absorption system imprinted on their spectra. From these spectra, we detect 13919 narrow C IV absorption systems whose absorption redshifts cover a range of z_abs_=1.8784-4.3704. In this paper and Paper I, we have selected 37241 appropriate quasars with median S/N>=4 and 1.54<~z_em_<~5.16 to visually analyze narrow CIV{lambda}{lambda}1548,1551 absorption doublets one by one. A total of 15999 quasars are found to have at least one appropriate absorption system imprinted on their spectra. From these 15999 quasar spectra, we have detected 23336 appropriate CIV{lambda}{lambda}1548,1551 absorption systems with W_r_>=0.2{AA} whose absorption redshifts cover a range of z_abs_=1.4544-4.3704. The largest values of W_r_ are 3.19{AA} for the {lambda}1548 absorption line and 2.93{AA} for the {lambda}1551 absorption line, respectively. We find that only a few absorbers show large values of W_r_. About 1.1% of the total absorbers have W_r_{lambda}1548>=2.0{AA}.
98. BOSS narrow CIV absorption lines. I. zem<=2.4
ID:
ivo://CDS.VizieR/J/ApJS/210/7
Title:
BOSS narrow CIV absorption lines. I. zem<=2.4
Short Name:
J/ApJS/210/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have assembled absorption systems by visually identifying CIV {lambda}{lambda}1548, 1551 absorption doublets in the quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS) one by one. This paper is the first of the series of work. In this paper, we focus on quasars with relatively low redshifts and high signal-to-noise ratio spectra, and hence we limit our analysis to quasars with z_em_<=2.4 and to doublets with W_r_{lambda}1548>=0.2{AA}. Out of the more than 87000 quasars in Data Release 9, we limit our search to 10121 quasars that have the appropriate redshifts and spectra with high enough signal-to-noise ratios to identify narrow CIV absorption lines. Among them, 5442 quasars are detected to have at least one CIV {lambda}{lambda}1548, 1551 absorption doublet. We obtain a catalog containing 8368 CIV {lambda}{lambda}1548, 1551 absorption systems, whose redshifts are within z_abs_=1.4544-2.2805. In this catalog, about 33.7% absorbers have 0.2{AA}<=W_r_{lambda}1548<0.5{AA}, about 45.9% absorbers have 0.5{AA}<=W_r_{lambda}1548<1.0{AA}, about 19.2% absorbers have 1.0{AA}<=W_r_{lambda}1548<2.0{AA}, and about 1.2% absorbers have W_r_{lambda}1548>=2.0{AA}.
99. BOSS: quasar luminosity function
ID:
ivo://CDS.VizieR/J/ApJ/773/14
Title:
BOSS: quasar luminosity function
Short Name:
J/ApJ/773/14
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22301 i<~21.8 quasars are selected over an area of 2236deg^2^, with confirmed spectroscopic redshifts between 2.2<z<3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. The completeness of the survey is derived through simulated quasar photometry, and this completeness estimate is checked using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar K-correction. We probe the faint end of the QLF to M_i_(z=2.2){approx}-24.5 and see a clear break in the QLF at all redshifts up to z=3.5. A log-linear relation (in log{Phi}*-M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2<z<3.5; across this interval the break luminosity increases by a factor of ~2.6 while {Phi}* declines by a factor of ~8. At z<~2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of "AGN downsizing" is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.
100. B0355+508 reduced spectra
ID:
ivo://CDS.VizieR/J/A+A/633/A54
Title:
B0355+508 reduced spectra
Short Name:
J/A+A/633/A54
Date:
21 Oct 2021
Publisher:
CDS
Description:
Phosphorus-bearing species are essential to the formation of life on Earth, however they have barely been detected in the interstellar medium. In particular, towards star-forming regions only PN and PO have been identified so far. Since only a small number of detections of P-bearing molecules are available, their chemical formation pathways are not easy to constrain and are thus highly debatable. An important factor still missing in the chemical models is the initial elemental abundance of phosphorus, that is, the depletion level of P at the start of chemical models of dense clouds. In order to overcome this problem, we study P-bearing species in diffuse and translucent clouds. In these objects phosphorus is expected to be mainly in the gas phase and therefore the elemental initial abundance needed in our chemical simulations corresponds to the cosmic one and is well constrained. For the study of P-bearing chemistry we used an advanced chemical model. We updated and significantly extended the P-chemistry network based on chemical databases and previous literature. We performed single-pointing observations with the IRAM 30m telescope in the 3mm range towards the line of sight to the strong continuum source B0355+508 aiming for the (2-1) transitions of PN, PO, HCP, and CP. This line of sight incorporates five diffuse and/or translucent clouds. The (2-1) transitions of the PN, PO, HCP, and CP were not detected. We report high signal-to-noise-ratio detections of the (1-0) lines of ^13^CO, HNC, and CN along with a first detection of C^34^S towards this line of sight. We have attempted to reproduce the observations of HNC, CN, CS, and CO in every cloud with our model by applying typical physical conditions for diffuse or translucent clouds. We find that towards the densest clouds with v_LSR_= -10, -17 km/s the best-fit model is given by the parameters (n_H_, A_V_, T_gas_) = (300cm^-3^, 3mag, 40K). According to our best-fit model, the most abundant P-bearing species are HCP and CP (1e-10). The molecules PN, PO, and PH_3_ also show relatively high predicted abundances of 1e-11. We show that the abundances of these species are sensitive to visual extinction, cosmic-ray ionization rate, and the diffusion-to-desorption energy ratio on dust grains. The production of P-bearing species is favored towards translucent rather than diffuse clouds, where the environment provides a stronger shielding from the interstellar radiation. Based on our improved model, we show that the (1-0) transitions of HCP, CP, PN, and PO are expected to be detectable with estimated intensities of up to ~200mK.