相关论文: On the universal validity of Case B recombination …
A recent study has claimed that the rotation curve shapes and mass densities of Low Surface Brightness (LSB) galaxies are largely consistent with $\Lambda$CDM predictions, in contrast to a large body of observational work. I demonstrate…
Aiming at the detection of cosmological gas being accreted onto galaxies of the local Universe, we examined the Halpha emission in the halo of 164 galaxies in the field of view of the Multi-Unit Spectroscopic Explorer Wide survey (\musew )…
An important constraint for galaxy evolution models is how much gas resides in galaxies, in particular at the peak of star formation z=1-3. We attempt a novel approach by letting long-duration Gamma Ray Bursts (LGRBs) x-ray their host…
Various theoretical models predict the existence of extended $\gamma$-ray halo around normal galaxies that could be produced by interactions of cosmic rays with the circumgalactic medium or by annihilation or decay of hypothetical dark…
We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, \tau^f_B, and the stellar mass surface density, \mu_{*}, of nearby (z < 0.13) spiral galaxies: log(\tau^f_B) =…
We put stringent constraints for the first time on the dust properties in the circumburst medium of a gamma-ray burst (GRB) afterglow. This is based on the optical spectrum of GRB 020813 (z=1.255), obtained with Keck I LRIS 4.65 h after the…
He II Ly-alpha 304/H-alpha 1640 emission lines are mainly produced by recombination, and their canonical ratio of about 10 may be a sensitive reddening indicator. We obtain the high S/N optical spectra of two quasars and combine them with…
We present a multi-wavelength study (BVRI band photometry and HI line interferometry) of nine late-type galaxies selected from the HIPASS Bright Galaxy Catalog on the basis of apparently high HI mass-to-light ratios (3 M_sun/L_sun <…
We use 2MASS photometry to select blue horizontal branch (BHB) candidates covering the sky |b|>15 deg. A 12.5<J<15.5 sample of BHB stars traces the thick disk and inner halo to d<9 kpc, with a density comparable to that of M giant stars. We…
We present new spectra of dominant galaxies in X-ray selected clusters, which combine with our previously published spectra to form a sample of 256 dominant galaxies in 215 clusters; 177 of these are members of the ROSAT Brightest Cluster…
Using a sample of nearly half a million galaxies, intersected by over 8 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we extend our previous study of the recombination radiation emitted by the gaseous halos of…
Sirius B is the nearest and brightest of all white dwarfs, but it is very difficult to observe at visible wavelengths due to the overwhelming scattered light contribution from Sirius A. However, from space we can take advantage of the…
The southern Galactic plane has been mapped at optical wavelengths and at under one-arcsecond angular resolution by the VST Photometric Ha Survey of the Galactic plane and bulge (VPHAS+). Anticipating the release of a uniform photometric…
The nebular recombination line H$\alpha$ is widely used as a star-formation rate (SFR) indicator in the local and high-redshift Universe. We present a detailed H$\alpha$ radiative transfer study of high-resolution isolated Milky-Way and…
From UV spectra of the bright quasar PHL 1811 recorded by FUSE and the E140M configuration on STIS, we have determined the abundances of various atomic species in a Lyman limit system at z = 0.0809 with log N(H I) = 17.98. Considerably more…
It is known that the diffuse H-alpha emission outside of bright H II regions not only are very extended, but also can occur in distinct patches or filaments far from H II regions, and the line ratios of [S II] 6716/H-alpha and [N II]…
Quasar lines of sight intersect intervening galaxy discs or circum-galactic environments at random impact parameters and potential well depths. Absorption line velocity widths ($\Delta v_{90}$) are known to scale with host galaxy stellar…
The hydrogen Balmer decrement (e.g., $\rm H\alpha/H\beta$) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs (LLAGNs) and changing-look AGNs…
(Abridged) Despite the privileged position that Lyman-alpha (Lya) emission line holds in the exploration of the distant universe and modern observational cosmology, the origin of the observed diversity of lya profiles remains to be…
Here we built up a sample of 22 GRBs at redshifts $z > 2$ observed with X-shooter to determine the abundances of hydrogen, metals, dust, and molecular species. This allows us to study the metallicity and dust depletion effects in the…