- ID:
- ivo://CDS.VizieR/J/ApJ/728/23
- Title:
- GALEX UV-bright high-redshift quasars
- Short Name:
- J/ApJ/728/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the small population of high-redshift (z_em_>2.7) quasars detected by the Galaxy Evolution Explorer(GALEX), whose far-UV emission is not extinguished by intervening HI Lyman limit systems. We correlate almost all verified z_em_>2.7 quasars to the GALEX GR4 source catalog covering ~25000deg^2^, yielding 304 sources detected at signal-to-noise ratio (S/N)>3. However, ~50% of these are only detected in the GALEX NUV band, signaling the truncation of the FUV flux by low-redshift optically thick Lyman limit systems. We regard 52 quasars detected at S/N>3 to be most promising for Hubble Space Telescope follow-up, with an additional 114 quasars if we consider S/N>2 detections in the FUV. Combining the statistical properties of HI absorbers with the Sloan Digital Sky Survey (SDSS) quasar luminosity function, we predict a large all-sky population of ~200 quasars with z_em_>2.7 and i<~19 that should be detectable at the HeII edge at m_304_<21. However, SDSS provides just half of the NUV-bright quasars that should have been detected by SDSS and GALEX. With mock quasar photometry we revise the SDSS quasar selection function, finding that SDSS systematically misses quasars with blue u-g<~2 colors at 3<~z_em_<~3.5 due to overlap with the stellar locus in color space.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/237/11
- Title:
- Gal. redshift survey near HST/COS AGN sight lines
- Short Name:
- J/ApJS/237/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To establish the connection between galaxies and UV-detected absorption systems in the local universe, a deep (g<=20) and wide (~20' radius) galaxy redshift survey is presented around 47 sight lines to UV-bright AGNs observed by the Cosmic Origins Spectrograph (COS). Specific COS science team papers have used this survey to connect absorbers to galaxies, groups of galaxies, and large-scale structures, including voids. Here we present the technical details of the survey and the basic measurements required for its use, including redshifts for individual galaxies and uncertainties determined collectively by spectral class (emission-line, absorption-line, and composite spectra) and completeness for each sight line as a function of impact parameter and magnitude. For most of these sight lines, the design criteria of >90% completeness over a >1Mpc region down to <~0.1L* luminosities at z<=0.1 allows a plausible association between low-z absorbers and individual galaxies. Ly{alpha} covering fractions are computed to approximate the star-forming and passive galaxy populations using the spectral classes above. In agreement with previous results, the covering fraction of star-forming galaxies with L>=0.3L* is consistent with unity inside one virial radius and declines slowly to >50% at four virial radii. On the other hand, passive galaxies have lower covering fractions (~60%) and a shallower decline with impact parameter, suggesting that their gaseous halos are patchy but have a larger scale-length than star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/30
- Title:
- Gamma-ray burst flares: X-ray flaring
- Short Name:
- J/ApJ/788/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 498 flaring periods found in gamma-ray burst (GRB) light curves taken from the online Swift X-Ray Telescope GRB Catalogue (Evans et al. 2007A&A...469..379E, 2009, J/MNRAS/397/1177). We analyzed 680 individual light curves using a flare detection method developed and used on our UV/optical GRB Flare Catalog. This method makes use of the Bayesian Information Criterion to analyze the residuals of fitted GRB light curves and statistically determines the optimal fit to the light curve residuals in an attempt to identify any additional features. These features, which we classify as flares, are identified by iteratively adding additional "breaks" to the light curve. We find evidence of flaring in 326 of the analyzed light curves. For those light curves with flares, we find an average number of ~1.5 flares per GRB. As with the UV/optical, flaring in our sample is generally confined to the first 1000 s of the afterglow, but can be detected to beyond 10^5^ s. Only ~50% of the detected flares follow the "classical" definition of {Delta}t/t<=0.5, with many of the largest flares exceeding this value.
- ID:
- ivo://CDS.VizieR/J/ApJ/609/935
- Title:
- Gamma-ray burst formation rate
- Short Name:
- J/ApJ/609/935
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate a gamma-ray burst (GRB) formation rate based on the new relation between the spectral peak energy (E_p_) and the peak luminosity. The new relation is derived by combining the data of E_p_ and the peak luminosities by BeppoSAX and BATSE, and it looks considerably tighter and more reliable than the relations suggested by the previous works. Using the new E_p_-luminosity relation, we estimate redshifts of the 689 GRBs without known distances in the BATSE catalog and derive a GRB formation rate as a function of the redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/90
- Title:
- Gamma-ray bursts minimum timescales
- Short Name:
- J/ApJ/787/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time - due to the presence of a large number of GRBs with measured redshift - determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of {Delta}t_min_=0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3x10^3^ km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.
- ID:
- ivo://CDS.VizieR/J/ApJ/726/16
- Title:
- {gamma}-ray loud blazars
- Short Name:
- J/ApJ/726/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong {gamma}-ray emission. At lower flux levels, radio flux density does not directly correlate with {gamma}-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the {gamma}-ray loud and quiet FSRQs can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the {gamma}-ray loud FSRQs are fundamentally different from the {gamma}-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for {gamma}-ray loud AGNs.
- ID:
- ivo://CDS.VizieR/J/A+A/462/875
- Title:
- Garching-Bonn Deep Survey (GaBoDS) IX
- Short Name:
- J/A+A/462/875
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of the present work is the construction of a mass-selected galaxy cluster sample based on weak gravitational lensing methods. This sample will be subject to spectroscopic follow-up observations. We apply the mass aperture statistics (S-statistics) and a new derivative of it (the P-statistics) to 19 square degrees of high quality, single colour wide field imaging data obtained with the WFI@MPG/ESO 2.2m telescope. For the statistics a family of filter functions is used that approximates the expected tangential radial shear profile and thus allows for the efficient detection of mass concentrations. The exact performance of the P-statistics still needs to be evaluated by means of simulations.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A109
- Title:
- Gas kinematics of spiral galaxies
- Short Name:
- J/A+A/520/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We trace the interaction processes of galaxies at intermediate redshift by measuring the irregularity of their ionized gas kinematics, and investigate these irregularities as a function of the environment (cluster versus field) and of morphological type (spiral versus irregular). We obtain the gas velocity fields by placing three parallel and adjacent VLT/FORS2 slits on each galaxy. To quantify irregularities in the gas kinematics, we use three indicators: the standard deviation of the kinematic position angle ({sigma}_PA_), the mean deviation of the line of sight velocity profile from the cosine form which is measured using high order Fourier terms (k_3,5_/k_1_) and the average misalignment between the kinematical and photometric major axes ({Delta}{phi}). These indicators are then examined together with some photometric and structural parameters (measured from HST and FORS2 images in the optical) such as the disk scale length, rest-frame colors, asymmetry, concentration, Gini coefficient and M20 . Our sample consists of 92 distant galaxies. 16 cluster (z~0.3 and z~0.5) and 29 field galaxies (0.10<=z<=0.91, mean z=0.44) of these have velocity fields with sufficient signal to be analyzed. To compare our sample with the local universe, we also analyze a sample from the SINGS survey.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/13
- Title:
- GASP. XXI. Star forming rate in 54 galaxies
- Short Name:
- J/ApJ/899/13
- Date:
- 15 Mar 2022 08:27:30
- Publisher:
- CDS
- Description:
- Using MUSE observations from the GASP survey, we study 54 galaxies undergoing ram pressure stripping (RPS) and spanning a wide range in galaxy mass and host cluster mass. We use this rich sample to study how the star formation rate (SFR) in the tails of stripped gas depends on the properties of the galaxy and its host cluster. We show that the interplay between all the parameters involved is complex and that there is not a single, dominant one in shaping the observed amount of SFR. Hence, we develop a simple analytical approach to describe the mass fraction of stripped gas and the SFR in the tail, as a function of the cluster velocity dispersion, galaxy stellar mass, clustercentric distance, and speed in the intracluster medium. Our model provides a good description of the observed gas truncation radius and of the fraction of SFR observed in the stripped tails, once we take into account the fact that the star formation efficiency in the tails is a factor of ~5 lower than in the galaxy disk, in agreement with GASP ongoing HI and CO observations. Finally, we estimate the contribution of RPS to the intracluster light (ICL) and find that the average SFR in the tails of ram pressure stripped gas is ~0.22M{odot}/yr per cluster. By extrapolating this result to evaluate the contribution to the ICL at different epochs, we compute an integrated average value per cluster of ~4x109M{sun} of stars formed in the tails of RPS galaxies since z~1.
- ID:
- ivo://CDS.VizieR/J/ApJ/895/106
- Title:
- GAs Stripping Phenomena in galaxies with MUSE
- Short Name:
- J/ApJ/895/106
- Date:
- 15 Mar 2022 07:48:07
- Publisher:
- CDS
- Description:
- Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP) survey, we study the gas-phase metallicity scaling relations of a sample of 29 cluster galaxies undergoing ram pressure stripping and of a reference sample of (16 cluster and 16 field) galaxies with no significant signs of gas disturbance. We adopt the pyqz code to infer the mean gas metallicity at the effective radius and achieve a well-defined mass-metallicity relation (MZR) in the stellar mass range 10^9.25^<=M_*_<=10^11.5^M{odot} with a scatter of 0.12dex. At any given mass, reference cluster and stripping galaxies have similar metallicities, while the field galaxies with M_*_<1010.25M{sun} show on average lower gas metallicity than galaxies in clusters. Our results indicate that at the effective radius, the chemical properties of the stripping galaxies are independent of the ram pressure stripping mechanism. Nonetheless, at the lowest masses, we detect four stripping galaxies well above the common MZR that suggest a more complex scenario. Overall, we find signs of an anticorrelation between the metallicity and both the star formation rate and the galaxy size, in agreement with previous studies. No significant trends are instead found with the halo mass, clustercentric distance, and local galaxy density in clusters. In conclusion, we advise a more detailed analysis of the spatially resolved gas metallicity maps of the galaxies, able to highlight effects of gas redistribution inside the disk due to ram pressure stripping.
