A5026672942- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Scientific Research and Discoveries
- Radio Astronomy Observations and Technology
- Computational Physics and Python Applications
- Pulsars and Gravitational Waves Research
- Particle Accelerators and Free-Electron Lasers
Case Western Reserve University
2015-2023
Indiana University Bloomington
2014-2019
We characterise the radial density, metallicity and flattening profile of Milky Way's stellar halo, based on large sample 1757 spectroscopically confirmed giant stars from SDSS/SEGUE-2 after excising that were algorithmically attributed to apparent halo substructure (including Sagittarius stream). Compared BHB or RR Lyrae, giants are more readily understood tracers overall star population, with less bias in age metallicity. The well-characterized selection function enables forward modelling...
Abstract We present a sample of 115 very low optical surface brightness, highly extended, H i -rich galaxies carefully selected from the ALFALFA survey that have similar absolute magnitudes, brightnesses, and radii to recently discovered “ultra-diffuse” (UDGs). However, these systems are bluer more irregular morphologies than other UDGs, isolated, contain significant reservoirs . find while sources normal star formation rates for -selected stellar mass, they efficiencies. further deep...
Abstract The Sloan Extension for Galactic Understanding and Exploration 2 (SEGUE-2) obtained 128,288 low-resolution spectra ( R ∼ 1800) of 118,958 unique stars in the first year Digital Sky Survey III (2008–2009). SEGUE-2 targeted prioritized distant halo tracers (blue horizontal-branch stars, K giants, M giants) metal-poor or kinematically hot populations. main goal was to target measure their kinematics chemical abundances learn about formation evolution Milky Way. We present field...
We report the discovery and follow-up observations of a system three objects identified by ALFALFA extragalactic HI survey, cataloged as (almost) dark sources, i.e., detections with no discernible counterpart in publicly available, wide-field, imaging surveys. have obtained deep optical WIYN pODI synthesis maps WSRT HI1232+20 system. The source highest flux has newly discovered ultra-low surface brightness (LSB) associated it, while other two sources detected counterparts our images. Our...
ABSTRACT We statistically quantify the amount of substructure in Milky Way stellar halo using a sample 4568 K giant stars at Galactocentric distances ranging over 5–125 kpc. These have been selected photometrically and confirmed spectroscopically as giants from Sloan Digital Sky Survey’s Extension for Galactic Understanding Exploration project. Using position–velocity clustering estimator (the 4distance) model smooth halo, we divided by distance metallicity. Overall, find that whole is...
We present neutral hydrogen (HI) imaging observations with the Westerbork Synthesis Radio Telescope of AGC198606, an HI cloud discovered in ALFALFA 21cm survey. This object is particular note as it located 16 km/s and 1.2 degrees from gas-bearing ultra-faint dwarf galaxy Leo T while having a similar linewidth approximately twice flux density. The reveal smooth, undisturbed morphology full extent 23'x16' at 5x10^18 atoms cm^-2 level. velocity field AGC198606 shows ordered motion gradient ~25...
Abstract We present results from the analysis of WIYN pODI imaging 23 ultracompact high-velocity clouds (UCHVCs), which were identified in ALFALFA H i survey as possible dwarf galaxies or near Local Group. To search for a resolved stellar population associated with gas these objects, we carried out series steps designed to identify overdensities our optical images. five objects that are likely counterparts UCHVCs, at distances ∼350 kpc ∼1.6 Mpc. Two already described Janesh et al.; estimated...
We present Arecibo, GBT, VLA and WIYN/pODI observations of the ALFALFA source AGC 226067. Originally identified as an ultra-compact high velocity cloud candidate Local Group galaxy, 226067 is spatially kinematically coincident with Virgo cluster, identification by multiple groups optical counterpart no resolved stars supports interpretation that this systems lies at distance (D=17 Mpc). The combined reveal system consists components: a central HI associated (AGC 226067), smaller HI-only...
We report on initial results from a campaign to obtain optical imaging of sample Ultra Compact High Velocity Clouds (UCHVCs) discovered by the ALFALFA neutral hydrogen (HI) survey. UCHVCs are sources with velocities and sizes consistent their being low-mass dwarf galaxies in Local Volume, but without counterparts existing catalogs. using WIYN 3.5-m telescope pODI camera image these objects search for an associated stellar population. In this paper, we present our observational strategy...
We present new high-resolution HI spectral line imaging of Coma P, the brightest source in system 1232$+$20. This extremely low surface brightness galaxy was first identified ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic with no obvious optical counterpart existing data (although faint ultraviolet emission detected archival GALEX imaging). Using combination from Westerbork Synthesis Radio Telescope and Karl G. Jansky Very Large Array, we investigate morphology...
Abstract We present results from deep H i and optical imaging of AGC 229101, an unusual source detected at v helio =7116 km s −1 in the Arecibo Legacy Fast ALFA (ALFALFA) blind survey. Initially classified as a candidate “dark” because it lacks clear counterpart Sloan Digital Sky Survey (SDSS) or Digitized 2 (DSS2) imaging, 229101 has 10 9.31±0.05 M ⊙ , but line width only 43 ± 9 . Low-resolution Westerbork Synthesis Radio Telescope (WSRT) higher-resolution Very Large Array (VLA) B-array...
We report on the detection at $>$98% confidence of an optical counterpart to AGC 249525, Ultra-Compact High Velocity Cloud (UCHVC) discovered by ALFALFA blind neutral hydrogen survey. UCHVCs are compact, isolated HI clouds with properties consistent their being nearby low-mass galaxies, but without identified counterparts in extant surveys. Analysis resolved stellar sources deep $g$- and $i$-band imaging from WIYN pODI camera reveals a clustering possible Red Giant Branch stars associated...
Abstract We present results from an optical search for Local Group dwarf galaxy candidates associated with the Ultra-Compact High Velocity Clouds (UCHVCs) discovered by ALFALFA neutral hydrogen survey. The UCHVCs are isolated, compact H i clouds projected sizes, velocities, and estimated masses that suggest they may be nearby galaxies, but have no clear counterpart in existing survey data. observed 26 WIYN 3.5 m telescope One Degree Imager (ODI) two broadband filters searched images resolved...
Abstract The combination of sensitivity and large sky coverage the ALFALFA HI survey has enabled detection difficult to observe low mass galaxies in numbers, including dwarf overlooked optical surveys. Three different, but connected, studies from are particular interest: SHIELD (Survey Extremely Low-mass Dwarfs), candidate gas-rich ultra-faint galaxies, (Almost) Dark population. is a systematic multiwavelength study all with M < 10 7.2 ⊙ clear counterparts. Candidate extend galaxy...