Related papers: Imaging Redshift Estimates for Fermi BL Lacs
The redshift distribution of the short-duration GRBs is a crucial, but currently fragmentary, clue to the nature of their progenitors. Here we present optical observations of nine short GRBs obtained with Gemini, Magellan, and the Hubble…
We present the results of ground-based and HST imaging studies targeted on z>4.5 quasar fields. High-redshift galaxies identified in deep narrow-band Lyman alpha images of the fields surrounding the quasars BR1202-0725 (z=4.694) and…
PKS 1424+240 is a BL-Lac blazar with unknown redshift detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. It was first detected at very-high-energy by VERITAS and latter confirmed by MAGIC. Attempts to find limits on its…
Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with WFC3/IR onboard the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star forming…
Spectroscopic observations of a sample of 42 flat-spectrum radio sources from the Cosmic Lens All-Sky Survey (CLASS) have yielded a mean redshift of $<z> = 1.27$ with an RMS spread of 0.95, at a completeness level of 64%. The sample…
Fermi can measure the spectral properties of gamma-ray bursts over a very large energy range and is opening a new window on the prompt emission of these energetic events. Localizations by the instruments on Fermi in combination with…
We have recently proposed a new simplified scenario where blazars are classified as flat-spectrum radio quasars (FSRQs) or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted radiation…
The BL-Lac family of active galaxies possess almost featureless spectra and exhibit rapid variability over their entire spectral range. A number of models have been developed to explain these extreme properties, several of which have…
We present rest-frame UV and Ly-alpha images of spatially-resolved structures around five high-redshift radio-loud quasars obtained with the WFPC2 camera on the Hubble Space Telescope. We find that all five quasars are extended and this…
We study the possible detection of and properties of very high-energy (VHE) gamma-ray emission (in the energy band above 100 GeV) from high redshift sources. We report on the detection of VHE gamma-ray flux from blazars with redshifts…
We present 10 new gamma-ray burst (GRB) redshifts and another five redshift limits based on host galaxy spectroscopy obtained as part of a large program conducted at the Very Large Telescope (VLT). The redshifts span the range 0.345 < z <…
We present the techniques used to determine redshifts and to characterize the spectra of objects in the Caltech Faint Galaxy Redshift Survey in terms of spectral classes and redshift quality classes. These are then applied to spectra from…
We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the $z$=6.3 quasar SDSS J1030+0525. This is currently the fifth deepest X-ray field, and reaches a 0.5-2 keV flux…
RGB J2243+203 is a blazar at an estimated redshift of greater than 0.39 that has been classified both as an intermediate-frequency-peaked BL Lac object and as a high-frequency-peaked BL Lac object. This source has been detected by VERITAS…
We present analysis of a new flux limited sample of 72 X-ray selected BL Lacertae objects with known redshifts for 59 of them. We find the more X-ray dominated BL Lac having negative evolution with redshift, while intermediate objects show…
We present optical spectroscopy data that allowed a measurement of the redshift for the X-ray selected BL Lacertae object 1517+656. With a redshift of z = 0.702 this object has an absolute magnitude of B = -26.4 and is also an extremely…
We have compiled a sample of $\sim 9600$ bright, $i\le 18.95$, red, $b_j-r>2$, candidate galaxies in an area of 220 deg$^2$. These are luminous, $L > L^*$, field early-type galaxies with redshifts $0.3 \la z \la 0.6$. We present a redshift…
We present the results of a high resolution (0.27 arcsec/px) near-infrared H band (1.65 micron) imaging survey of a complete sample of 20 flat spectrum radio quasars (FSRQ) extracted from the 2Jy catalogue of radio sources. The observed…
BL Lacertae (Lac) objects that are detected at very-high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the…
In October 2024, the object BL Lacertae experienced the brightest flaring event in gamma-ray ($>$100 MeV) with a historically bright $\gamma$-ray flux of $\sim$2.59 $\times 10^{-5}$ erg cm$^{-2}$ s$^{-1}$ with a detection of a 175.7 GeV…