Related papers: Extended Light in E/S0 Galaxies and Implications f…
ABRIDGED- The UV-optical color magnitude diagram (CMD) of rich galaxy groups is characterised by a well developed Red Sequence (RS), a Blue Cloud (BC) and the so-called Green Valley (GV). Loose, less evolved groups of galaxies likely not…
Recent observations of metal-poor, star-forming dwarf galaxies reveal He III regions, traced by nebular He II 4686 emission that require a strong source of extreme-ultraviolet (EUV) radiation. The origin of this hard ionizing radiation…
The rest-frame UV emission from massive stars contains a wealth of information about the physical nature and conditions of star formation in galaxies. Using studies of the rest-frame UV, the past decade has witnessed the beginning of…
The Galaxy Evolution Explorer (GALEX) satellite performed the first and only large-area UV survey, which in tandem with the Sloan Digital Sky Survey (SDSS) has facilitated modeling of the spectral energy distributions (SEDs) of low-redshift…
Using data from the ROSAT Wide Field Camera all-sky survey, we have established upper limits to the extreme ultraviolet (EUV) flux from a sample of 30 bright, nearby, non-active spiral galaxies. These galaxies were chosen to be those most…
We investigate models for the class of ultraluminous non-nuclear X-ray sources (ULXs) seen in a number of galaxies and probably associated with star-forming regions. Models where the X-ray emission is assumed to be isotropic run into…
The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color, i.e. the IRX-UV relation, was regarded as a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation…
Most of the massive star-forming galaxies are found to have `inside-out' stellar mass growth modes, which means the inner parts of the galaxies mainly consist of the older stellar population, while the star forming in the outskirt of the…
ABRIDGED: We use HSTACS and NICMOS imaging to study the structure and colors of a sample of nine late-type spirals. We find: (1) A correlation between bulge and disks scale-lengths, and a correlation between the colors of the bulges and…
The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in H-alpha and ultraviolet. Using a sample of…
We study the sizes of galaxies in the Epoch of Reionization using a sample of ~100,000 galaxies from the BlueTides cosmological hydrodynamical simulation from z=7 to 11. We measure the galaxy sizes from stellar mass and luminosity maps,…
Shell galaxies are widely considered the debris of recent accretion/merging episodes. Their high frequency in low density environment suggests that such episodes could be among the driver of the early-type galaxy secular evolution. We…
Recent JWST observations suggest that galaxies at z > 9 may be dominated by low-opacity SNe-produced dust before efficient ISM grain growth is established. This transition in dust origin and opacity could explain both the prevalence of…
Most of the mass in protoplanetary disks is in the form of gas. The study of the gas and its diagnostics is of fundamental importance in order to achieve a detailed description of the thermal and chemical structure of the disk. The…
In the last few years, prominent high-ionization nebular emission lines (i.e., OIII], CIII], CIV, HeII) have been observed in the deep UV spectra of z~5-7 galaxies, indicating that extreme radiation fields characterize reionization-era…
We present an analysis of the far-ultraviolet upturn phenomenon (UVX) observed in elliptical galaxies and spiral galaxy bulges. Our premise is that the UV radiation from these systems emanates primarily from extreme horizontal branch (EHB)…
CONTEXT:At low redshift, early-type galaxies often exhibit a rising flux with decreasing wavelength in the 1000-2500 \AA{} range, called "UV upturn". The origin of this phenomenon is debated, and its evolution with redshift is poorly…
JWST has enabled the detection of the UV continuum of galaxies at z>10, evidencing a population of extremely blue, potentially dust-free galaxies. Interpreting the UV spectra of galaxies as they redden is complicated by the well-known…
The diffuse ultraviolet background radiation has been mapped over most of the sky with 2\arcmin \ resolution using data from the \textit{GALEX} survey. We utilize this map to study the correlation between the UV background and clusters of…
We have searched for ultraluminous X-ray sources (ULXs) in a sample of 28 elliptical and S0 galaxies observed with Chandra. We find that the number of X-ray sources detected at a flux level that would correspond to a 0.3-10 keV X-ray…