相关论文: Ionization Sources of the Local Interstellar Cloud…

Two nearby B-type stars, $\epsilon$ CMa ($124\pm2$ pc) and $\beta$ CMa ($151\pm5$ pc), are important contributors to the photoionization of the local interstellar clouds. At spectral type B1 II-III, $\beta$ CMa is slightly hotter than…

This paper presents the study of the interstellar medium toward beta CMa, a disk sight-line known for its low neutral gas density. This study uses high and medium resolution HST-GHRS spectra including lines from many species. The line of…

We present new calculations of the photoionization of interstellar matter within ~5 pc of the Sun (which we refer to as the Complex of Local Interstellar Clouds or CLIC) by directly observed radiation sources including nearby hot stars and…

In this paper we use a number of observations to construct an integrated picture of the ionisation in the interiors of quiescent warm opaque interstellar clouds and in the intercloud medium (ICM) outside dense HII regions and hot dilute…

A disconcerting mismatch of thermal pressures for two media in contact with each other, (1) the warm, Circum-heliospheric Interstellar Medium (CHISM) and (2) the very hot material within a much larger region called the Local Bubble (LB),…

We discuss the sources which are likely to dominate the ionizing field throughout the Local Group. In terms of the limiting flux to produce detectable H-alpha emission (4-10 x 10**3 phot/cm**2/s), the four dominant galaxies (M31, Galaxy,…

FUSE spectra of the white dwarf stars G191-B2B, GD 394, WD 2211-495 and WD 2331-475 cover the absorption features out of the ground electronic states of N I, N II, N III, O I and Ar I in the far ultraviolet, providing new insights on the…

We use the recent detection of He II absorption at $z=2.2-2.6$ in the line of sight of the quasar HS1700+64 to put bounds on the sources of ionization. We find that given the uncertainty in $\tauhgp$ and the model of absorption in the…

The first stars and quasars are known sources of hard ionizing radiation in the first billion years of the Universe. We examine the joint effects of X-rays and hard UV radiation from such first-light sources on the hydrogen and helium…

The B2 star $\epsilon$ CMa, at parallax distance $d = 124\pm2$~pc, dominates the H I photoionization of the local interstellar cloud (LIC). At its closer parallax distance compared to previous estimates, $\epsilon$ CMa has a 0.9 mag fainter…

The spectrum of beta CMa (Mirzam) between 1000 and 1200 A was recorded at a wavelength resolving power ~ 60 000 by the Interstellar Medium Absorption Profile Spectrograph (IMAPS) during its orbital flight on the ORFEUS-SPAS II mission in…

Primordial stars are expected to be very massive and hot, producing copious amounts of hard ionizing radiation. The best place to study hard ionizing radiation in the local universe is in very metal-deficient Blue Compact Dwarf (BCD)…

The composition and physical properties of several local clouds, including the Local Interstellar Cloud (LIC) in which the Sun is embedded, are derived from absorption features in the UV spectrum of the star epsilon CMa. We derive…

We carry out a new suite of cosmological radiation hydrodynamic simulations and explore the relative impacts on reionization-epoch star formation of galactic outflows and photoionization heating. By itself, an extragalactic ultraviolet…

The H II region N88a in the Small Magellanic Cloud (SMC) is a spherical region of $1.5~\mathrm{pc}$ diameter, with high concentration of gas and dust, and at least four massive stars within it. Previous studies suggest that the four known…

We have recently identified several high velocity (V < -100 km/s) clouds in the directions of Mrk 509 and PKS 2155-304 that have unusual ionization properties. The clouds exhibit strong C IV absorption with little or no detectable low ion…

We present FUSE observations of the interstellar gas toward 30 white dwarf and 1 subdwarf (SdO) stars. These sightlines probe the Local Bubble (LB) and the local interstellar medium (LISM) near the LB. Our survey detected only diffuse H_2…

Resolution of nearby giant HII regions into their stellar and nebular constituents provides fundamental insights for interpreting more distant and powerful starburst activity. The following summarizes recent advances in our understanding of…

Suzaku observed the molecular cloud MBM12 and a blank field less than 3 degrees away to separate the local and distant components of the diffuse soft X-ray background. Towards MBM12, a local (D< 275 pc) O VII emission line was clearly…

Unidentified extreme UV sources, detected in the {\it EUVE} and {\it ROSAT} WFC all-sky surveys, could be isolated old neutron stars, accreting material from the ISM. The closest neutron stars, that are located in the local ISM bubble of…