Sameer
We present a spectroscopic and imaging analysis of the $z_{gal} \approx 1.1334$ ultra-strong MgII absorption system identified in the $VLT$/UVES spectrum of a background quasar located at $\rho \approx 18$ kpc from a star-forming galaxy.…
In this study, we explore the properties of diffuse intergalactic gas residing in the outskirts of the four nearby, low-mass galaxy groups NGC1052, NGC5866, NGC4631, and NGC3992 (all at cz<2000 km/s) beyond their group virial radii. Using…
We present the first results from the COS-EDGES survey, targeting the kinematic connection between the ISM and multi-phase circumgalactic medium (CGM) in nine isolated, edge-on galaxies at z~0.2, each probed along its major axis by a…
The inner circumgalactic medium (CGM) of galaxies, where disk and halo processes intersect, remains poorly characterized despite its critical role in regulating galaxy evolution. We present results from Project AMIGA Insider, mapping…
The multiphase CGM hosts critical processes that affect galaxy evolution such as accretion and outflows. We searched for evidence of these phenomena by using the EW co-rotation fraction ($f_{\rm EWcorot}$) to study the kinematic connection…
We analyze the \ovi\ content and kinematics for 126 {\hi}-selected absorbers at $0.14 \lesssim z \lesssim 0.73$ for which the metallicities of their cool photoionized phase have been determined. We separate the absorbers into 100 strong…
The CGM hosts many physical processes with different kinematic signatures that affect galaxy evolution. We address the CGM-galaxy kinematic connection by quantifying the fraction of HI that is aligned with galaxy rotation with the…
While most galaxies live in group environments where they undergo an accelerated evolution, the characteristics of their circumgalactic medium (CGM) remain uncertain. We present an analysis of the CGM of two galaxy groups in different…
The pervasive presence of warm gas in galaxy halos suggests that the circumgalactic medium (CGM) is multiphase in its ionization structure and complex in its kinematics. Some recent state-of-the-art cosmological galaxy simulations predict…
In the Halo21 absorption modeling challenge we generated synthetic absorption spectra of the circumgalactic medium (CGM), and attempted to estimate the metallicity, temperature, and density (Z, T, and nH) of the underlying gas using…
As part of our program to identify host galaxies of known z=2-3 MgII absorbers with the Keck Cosmic Web Imager (KCWI), we discovered a compact group giving rise to a z=2.431 DLA with ultra-strong MgII absorption in quasar field…
We present an absorption line study of the physical and chemical properties of the Leo HI Ring and the Leo I Group as traced by 11 quasar sightlines spread over a 600 kpc X 800 kpc region. Using HST/COS G130/G160 archival observations as…
Blazars are some of the brightest UV and X-ray sources in the sky and are valuable probes of the elusive warm-hot intergalactic medium (WHIM; $T{\simeq} 10^5-10^7$ K). However, many of the brightest blazars$-$called BL Lac objects such as…
We used adaptive mesh refinement hydrodynamic cosmological simulations of a $z=1$ Milky Way-type galaxy and a $z=0$ Dwarf galaxy and generated synthetic quasar absorption-line spectra of their circumgalactic medium (CGM). Our goal is to…
We present an analysis of the galaxy environment and physical properties of a partial Lyman limit system at z = 0.83718 with HI and metal line components closely separated in redshift space ($|\Delta v| \approx 400$ km/s) towards the…
We present a new method aimed at improving the efficiency of component by component ionization modeling of intervening quasar absorption line systems. We carry out cloud-by-cloud, multiphase modeling making use of CLOUDY and Bayesian…
We present the detection and analysis of a weak low-ionization absorber at $z = 0.12122$ along the blazar sightline PG~$1424+240$, using spectroscopic data from both $HST$/COS and STIS. The absorber is a weak Mg II analogue, with incidence…
Context. PKS 1510-089 is one of only a few flat spectrum radio quasars detected in the VHE (very-high-energy, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510-089 emission during a…
We report the discovery of disappearance of Mg ii, Al iii, C iv, and Si iv broad absorption lines (BALs) at the same velocity, accompanied by a new Civ BAL emerging at a higher velocity, in the quasar J0827+4252 at z = 2.038. This is the…
We report on an X-ray and optical/UV study of eight Broad Absorption Line (BAL) to non-BAL transforming quasars at $z\,\approx\,$1.7-2.2 over 0.29-4.95 rest-frame years with at least three spectroscopic epochs for each quasar from the SDSS,…