Related papers: Trimming Down the Willman 1 dSph
Beyond its goals related to the extragalactic universe, the Sloan Digital Sky Survey (SDSS) is an effective tool for identifying stellar objects with unusual spectral energy distributions. Here we report on the 53 new magnetic white dwarfs…
A sample of 4208 objects with magnitude 15 < g* < 22 and colors of main sequence A stars has been selected from 370 square degrees of Sloan Digital Sky Survey (SDSS) commissioning observations. The data is from two long, narrow stripes,…
Abridged: We estimate the distances to ~48 million stars detected by the Sloan Digital Sky Survey and map their 3D number density distribution in 100 < D < 20 kpc range over 6,500 deg^2 of sky. The data show strong evidence for a Galaxy…
We present optical spectroscopy and near-infrared photometry of 126 cool white dwarfs in the Sloan Digital Sky Survey (SDSS). Our sample includes high proper motion targets selected using the SDSS and USNO-B astrometry and a dozen…
Metal-deficient stars are important tracers for understanding the early formation of the Galaxy. Recent large-scale surveys with both photometric and spectroscopic data have reported an increasing number of metal-deficient stars whose…
This study reports on photometric results of a search for LSB galaxies in a 0.76deg^2 field centered on the HDF-S. We present results from photometric analysis of the derived sample galaxies and compare number densities to results of former…
Previously, we have shown in Li et al. (2018) that very weak $\gamma$-ray excesses ($\sim 2\sigma$) appear in some Milky Way dwarf spheroidal galaxies (dSphs, including candidates) and the combination analysis of 12 nearby dSphs yields a…
We present a spectroscopic analysis of nearly 8000 late-type dwarfs in the Sloan Digital Sky Survey. Using the Halpha emission line as an activity indicator, we investigate the fraction of active stars as a function of spectral type and…
Draco dwarf Spheroidal galaxy (dSph) is one of the nearest and the most dark matter dominated satellites of the Milky Way. We obtained multi-epoch near-infrared (NIR, $JHK_s$) observations of the central region of Draco dSph covering a sky…
Dwarf galaxies are valuable laboratories for dynamical studies related to dark matter and galaxy evolution, yet it is currently unknown just how physically extended their stellar components are. Satellites orbiting the Galaxy's potential…
Lyman-$\alpha$ spheres, i.e. regions around the first stars which are illuminated by Lyman-$\alpha$ photons and show 21cm absorption feature against the CMB, are smoking guns at the dawn of the reionization epoch. Though overwhelming radio…
We used data from the Data Release 1 (DR1) of the Sloan Digital Sky Survey (SDSS) in order to define a catalog of about 13,000 star-forming galaxies (SFG). We discuss the results of two projects. First, we matched our catalog against the…
We present a wide-field (4.5 deg^2) photometric and spectroscopic survey of the Leo I dwarf spheroidal (dSph) galaxy to explore its extended morphology and dynamics. As in previous papers in this series, we take advantage of photometry in…
Giant low-surface brightness (GLSB) galaxies are an extreme class of objects with very faint and extended gas-rich disks. Malin 1 is the largest GLSB galaxy known to date, but its formation is still poorly understood. We use VLT/MUSE IFU…
Tidal streams are highly sensitive to perturbations from passing dark matter (DM) subhalos and thus provide a means of measuring their abundance. In a recent paper, we analyzed the distribution of stars along the GD-1 stream with a…
We discuss the density and radial velocity distributions of over 3000 candidate RR Lyrae stars selected by various methods using Sloan Digital Sky Survey data for about 1000 deg^2 of sky. This is more than 20 times larger sample than…
During the APPLES parallel campaign, the HST Advanced Camera for Surveys has resolved a distant stellar system, which appears to be an isolated dwarf galaxy. It is characterized by a circularly symmetric distribution of stars with an…
We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from $\textit{Gaia}$ Data Release 2 (DR2) and in almost…
Magnetic fields have been detected in several hundred white dwarfs, with strengths ranging from a few kG to several hundred MG. Only a few of the known fields have a mean magnetic field modulus below about 1 MG. We are searching for new…
It remains challenging to systematically survey nearby diffuse dwarf galaxies and address the formation mechanism of this population distinguishing from regular ones. We carry out a pilot search for these galaxies in the COSMOS field using…