G. Dhungana
A5060607432- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- CCD and CMOS Imaging Sensors
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- SAS software applications and methods
- Pulsars and Gravitational Waves Research
- Scientific Research and Discoveries
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Statistical and numerical algorithms
- Cosmology and Gravitation Theories
- Advanced Fluorescence Microscopy Techniques
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Infrared Target Detection Methodologies
- Advanced Numerical Analysis Techniques
- Astrophysics and Star Formation Studies
- Nuclear physics research studies
- Calibration and Measurement Techniques
Southern Methodist University
2014-2024
Abstract The DESI Legacy Imaging Surveys ( http://legacysurvey.org/ ) are a combination of three public projects (the Dark Energy Camera Survey, the Beijing–Arizona Sky and Mayall z -band Survey) that will jointly image ≈14,000 deg 2 extragalactic sky visible from northern hemisphere in optical bands g , r using telescopes at Kitt Peak National Observatory Cerro Tololo Inter-American Observatory. combined survey footprint is split into two contiguous areas by Galactic plane. imaging...
The Dark Energy Spectroscopic Instrument (DESI) has embarked on an ambitious five-year survey to explore the nature of dark energy with spectroscopy 40 million galaxies and quasars. DESI will determine precise redshifts employ Baryon Acoustic Oscillation method measure distances from nearby universe z > 3.5, as well growth structure probe potential modifications general relativity. In this paper we describe significant instrumentation developed for survey. new includes a wide-field, 3.2-deg...
Abstract The Dark Energy Spectroscopic Instrument (DESI) is carrying out a five-year survey that aims to measure the redshifts of tens millions galaxies and quasars, including 8 million luminous red (LRGs) in redshift range 0.4 < z ≲ 1.0. Here we present selection DESI LRG sample assess its spectroscopic performance using data from Survey Validation (SV) first two months Main Survey. sample, selected g , r W 1 photometry Legacy Imaging Surveys, highly robust against imaging systematics....
Abstract We describe the spectroscopic data processing pipeline of Dark Energy Spectroscopic Instrument (DESI), which is conducting a redshift survey about 40 million galaxies and quasars using purpose-built instrument on 4 m Mayall Telescope at Kitt Peak National Observatory. The main goal DESI to measure with unprecedented precision expansion history universe baryon acoustic oscillation technique growth rate structure space distortions. Ten spectrographs three cameras each disperse light...
The Dark Energy Spectroscopic Instrument (DESI) was designed to conduct a survey covering 14,000 deg$^2$ over five years constrain the cosmic expansion history through precise measurements of Baryon Acoustic Oscillations (BAO). scientific program for DESI evaluated during month Survey Validation (SV) campaign before beginning full operations. This produced deep spectra tens thousands objects from each stellar (MWS), bright galaxy (BGS), luminous red (LRG), emission line (ELG), and quasar...
Abstract The Dark Energy Spectroscopic Instrument (DESI) completed its 5 month Survey Validation in 2021 May. Spectra of stellar and extragalactic targets from constitute the first major data sample DESI survey. This paper describes public release those spectra, catalogs derived properties, intermediate products. In total, includes good-quality spectral information 466,447 objects targeted as part Milky Way Survey, 428,758 Bright Galaxy 227,318 Luminous Red sample, 437,664 Emission Line...
Abstract A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10–20 minutes, each to a precision several microns, with reconfiguration time fewer than 2 minutes. Over next 5 yr, they will enable newly constructed Dark Energy Spectroscopic Instrument (DESI) measure spectra 35 million galaxies and quasars. DESI produce largest 3D map universe date expansion...
In 2021 May, the Dark Energy Spectroscopic Instrument (DESI) began a 5 yr survey of approximately 50 million total extragalactic and Galactic targets. The primary DESI dark-time targets are emission line galaxies (ELGs), luminous red (LRGs) quasars (QSOs). bright time, will focus on two surveys known as Bright Galaxy Survey (BGS) Milky Way (MWS). also observes selection "secondary" for bespoke science goals. This paper gives an overview publicly available pipeline (desitarget) used to...
Abstract The Dark Energy Spectroscopic Instrument (DESI) will precisely constrain cosmic expansion and the growth of structure by collecting ∼40 million extragalactic redshifts across ∼80% history one-third sky. Emission Line galaxy (ELG) sample, which comprise about all DESI tracers, be used to probe universe over 0.6 < z 1.6 range, including 1.1 is expected provide tightest constraints. We present target selection for Survey Validation (SV) Main ELG samples, relies on imaging Legacy...
The Dark Energy Spectroscopic Instrument (DESI) completed its five-month Survey Validation in May 2021. Spectra of stellar and extragalactic targets from constitute the first major data sample DESI survey. This paper describes public release those spectra, catalogs derived properties, intermediate products. In total, includes good-quality spectral information 466,447 objects targeted as part Milky Way Survey, 428,758 Bright Galaxy 227,318 Luminous Red sample, 437,664 Emission Line 76,079...
Abstract A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) optical spectroscopic data to quantify metrics. In this paper we present results from VI quasar using deep coadded SV spectra. We show that majority (≈70%) main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. nonnegligible fraction quasars misidentified by...
Abstract The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements galaxies to validate the final survey design and target selections. To assist in these tasks, we visually inspect DESI spectra approximately 2500 bright galaxies, 3500 luminous red (LRGs), 10,000 emission-line (ELGs) obtain robust redshift identifications. We then utilize inspected information characterize performance operation. Based on visual inspection (VI) catalogs, our...
ABSTRACT We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN 2012cg at 15 and 16 days before maximum B -band brightness. The emission is consistent with predictions impact of on a non-degenerate binary companion. This first companion to normal Ia. Sixteen light, <?CDATA $B-V$?> <?MML <mml:math> <mml:mi>B</mml:mi> <mml:mo>−</mml:mo> <mml:mi>V</mml:mi> </mml:math>?> color 0.2 mag bluer than other At later times, this has typical curve, extinction-corrected...
The Dark Energy Spectroscopic Instrument (DESI) was designed to conduct a survey covering 14,000 deg$^2$ over five years constrain the cosmic expansion history through precise measurements of Baryon Acoustic Oscillations (BAO). scientific program for DESI evaluated during month Survey Validation (SV) campaign before beginning full operations. This produced deep spectra tens thousands objects from each stellar (MWS), bright galaxy (BGS), luminous red (LRG), emission line (ELG), and quasar...
ABSTRACT We present the first detection of baryon acoustic oscillations (BAOs) signal obtained using unblinded data collected during initial 2 months operations Stage-IV ground-based Dark Energy Spectroscopic Instrument (DESI). From a selected sample 261 291 luminous red galaxies spanning redshift interval 0.4 &lt; z 1.1 and covering 1651 square degrees with 57.9 per cent completeness level, we report ∼5σ level BAO measurement location at precision 1.7 cent. Using bright galaxy 109 523...
We present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, 130215A / SN 2013ez 130831A 2013fu. In the case of 2013ez, we also spectroscopy at t-t0=16.1 d, which covers rest-frame 3000-6250 Angstroms. Based on Fe II (5169) Si (II) (6355), our spectrum indicates an unusually low expansion velocity 4000-6350 km/s, lowest ever measured a GRB-SN. Additionally, determined brightness shape each accompanying relative to template supernova (SN...
We present extensive optical ($UBVRI$, $g'r'i'z'$, and open CCD) near-infrared ($ZYJH$) photometry for the very nearby Type IIP SN ~2013ej extending from +1 to +461 days after shock breakout, estimated be MJD $56496.9\pm0.3$. Substantial time series ultraviolet spectroscopy obtained +8 +135 are also presented. Considering well-observed SNe literature, we derive $UBVRIJHK$ bolometric calibrations $UBVRI$ unfiltered measurements that potentially reach 2\% precision with a $B-V$ color-dependent...
ABSTRACT We present and validate the catalogue of Lyman-α forest fluctuations for 3D analyses using Early Data Release (EDR) from Dark Energy Spectroscopic Instrument (DESI) survey. used 88 511 quasars collected DESI Survey Validation (SV) data first two months main survey (M2). several improvements to method extract absorption performed in previous Sloan Digital Sky (SDSS). In particular, we modify weighting scheme show that it can improve precision correlation function measurement by more...
We report the first results of a high-redshift ($z$ >~ 5) quasar survey using Dark Energy Spectroscopic Instrument (DESI). As DESI secondary target program, this is designed to carry out systematic search and investigation quasars at $z$ 5, up redshift 6.8. The selection based on Legacy Imaging Surveys (the Surveys) DR9 photometry, combined with Pan-STARRS1 data $J$-band photometry from public surveys. A sample has been constructed Survey Validation 3 (SV3) first-year observations until May...
SN 2013df is a nearby Type IIb supernova that seems to be the spectroscopic twin of well-known 1993J. Previous studies revealed many, but not all interesting properties this event. Our goal was add new understanding both early and late-time phases 2013df. spectral analysis based on 6 optical spectra obtained with 9.2m Hobby-Eberly Telescope during first month after explosion, complemented by near-infrared spectrum. We applied SYNAPPS synthesis code constrain chemical composition physical...
Using synthetic Lyman-$\alpha$ forests from the Dark Energy Spectroscopic Instrument (DESI) survey, we present a study of impact errors in estimation quasar redshift on correlation functions. Estimates have large uncertainties few hundred $\text{km s}^{-1}\,$ due to broadness emission lines and intrinsic shifts other lines. We inject Gaussian random into mock catalogues, measure auto-correlation Lyman-$\alpha$-quasar cross-correlation find smearing BAO feature radial direction, but changes...
Abstract This paper presents data and analysis of SN 2010kd, a low-redshift ( z = 0.101) H-deficient superluminous supernova (SLSN), based on ultraviolet/optical photometry optical spectroscopy spanning between −28 +194 days relative to B -band maximum light. The light-curve comparison 2010kd with subset well-studied SLSNe I at comparable redshifts indicates that it is slow-decaying PTF12dam-like SLSN. Analytical modeling using the Minim code suggests bolometric light curve favors...