High‐resolution absorption spectroscopy of the circumgalactic medium of the Milky Way     

P. Richter  Aj. Fox  N. Ben Bekhti  M. T. Murphy  D. Bomans  S. Frank 《Astronomische Nachrichten》2014,335(1):92-98

In this article we discuss the importance of high‐resolution absorption spectroscopy for our understanding of the distribution and physical nature of the gaseous circumgalactic medium (CGM) that surrounds the Milky Way. Observational and theoretical studies indicate a high complexity of the gas kinematics and an extreme multi‐phase nature of the CGM in low‐redshift galaxies. High‐precision absorption‐line measurements of the Milky Way's gas environment thus are essential to explore fundamental parameters of circumgalactic gas in the local Universe, such as mass, chemical composition, and spatial distribution. We shortly review important characteristics of the Milky Way's CGM and discuss recent results from our multi‐wavelength observations of the Magellanic Stream. Finally, we discuss the potential of studying the warm‐hot phase of the Milky Way's CGM by searching for extremely weak [Fe X] λ 6374.5 Å and [Fe XIV] λ 5302.9 Å absorption in optical QSO spectra. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The Kα complex of He-like iron with dielectronic satellites     

Justin Oelgoetz  Anil K. Pradhan 《Monthly notices of the Royal Astronomical Society》2001,327(4):L42-L46

It is shown that the dielectronic satellites (DES) dominate X-ray spectral formation in the 6.7-keV K α complex of Fe  xxv at temperatures below that of maximum abundance in collisional ionization equilibrium T _m. Owing to their extreme temperature sensitivity, the DES are excellent spectral diagnostics for     in photoionized, collisional or hybrid plasmas; whereas the forbidden, intercombination and resonance lines of Fe  xxv are not. A diagnostic line ratio GD ( T ) is defined including the DES and the lines, with parameters from new relativistic atomic calculations. The DES absorption resonance strengths may be obtained from differential oscillator strengths, possibly to yield the     column densities. The DES contribution to highly ionized Fe should be of interest for models of redward broadening of K α features, ionized accretion discs, accretion flows and K α temporal-temperature variability in AGN.  相似文献   

Sextet transitions in Fe ii     

M. P. Donnelly  A. Hibbert 《Monthly notices of the Royal Astronomical Society》2001,321(2):247-253

We have calculated oscillator strengths for the J – J ' levels of the a  ⁶D– z  ⁶P^o, the a  ⁶D– z  ⁶D^o and the a  ⁶D– z  ⁶F^o multiplets in Fe  ii , using configuration interaction wave functions. The importance of the mixing of the ⁶P^o, ⁶D^o and ⁶F^o states is shown, as is the effect of core polarization of both the 3 p and 3 s orbitals. Good agreement with recent experimental results is obtained.  相似文献   

Silicon monosulphide radiative association     

C. M. Andreazza  E. P. Marinho 《Monthly notices of the Royal Astronomical Society》2007,380(1):365-368

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Understanding the atmospheric structure of T Tauri stars – II. UV spectroscopy of RY Tau, BP Tau, RU Lupi, GW Ori and CV Cha     

D.H. Brooks †  V.M. Costa  M.T.V.T. Lago  A.C. Lanzafame 《Monthly notices of the Royal Astronomical Society》2001,327(1):177-190

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用大气层结模型和反演法研究大气对毫米波吸收的改正     

向德琳  俞志尧 《中国天文和天体物理学报》1990,(4)

作者结合射电天文和气象实测资料,使用大气层结模型和反演法,数值计算了大气中云的含水量和云天大气对射电源毫米波辐射总衰减的改正。其结果优于均匀气温模型和两层大气模型的结果以及跟踪太阳法的结果。  相似文献   

The first detection of cobalt in a damped Lyman alpha system     

S.L. Ellison  S.G. Ryan  J.X. Prochaska 《Monthly notices of the Royal Astronomical Society》2001,326(2):628-636

The study of elemental abundances in damped Lyman alpha systems (DLAs) at high redshift represents one of our best opportunities to probe galaxy formation and chemical evolution at early times. By coupling measurements made in high- z DLAs with our knowledge of abundances determined locally and with nucleosynthetic models, we can start to piece together the star formation histories of these galaxies. Here, we discuss the clues to galactic chemical evolution that may be gleaned from studying the abundance of Co in DLAs. We present high resolution echelle spectra of two quasi-stellar objects (QSOs), Q2206−199 and Q1223+17, both already known to exhibit intervening damped systems. These observations have resulted in the first ever detection of Co at high redshift, associated with the z _abs=1.92 DLA in the sightline towards Q2206−199. We find that the abundance of Co is approximately 1/4 solar and that there is a clear overabundance relative to iron, [Co/Fe]=+0.31±0.05 . From the abundance of Zn, we determine that this is a relatively metal-rich DLA, with a metallicity of approximately 1/3 Z_⊙ . Therefore, this first detection of Co is similar to the marked overabundance relative to Fe seen in Galactic bulge and thick-disc stars.  相似文献   

The Second APM UKST Colour Survey for z > 4 quasars     

Lisa J. Storrie-Lombardi  Michael J. Irwin  Richard G. McMahon  Isobel M. Hook 《Monthly notices of the Royal Astronomical Society》2001,322(4):933-944

We present the spectra, positions, and finding charts for 31 bright ( R <19.3) colour-selected quasars covering the redshift range z =3.85–4.78, with four having redshifts z >4.5. The majority are in the southern sky ( δ <−25°). The quasar candidates were selected for their red ( B _J− R ≳2.5) colours from UK or POSSII Schmidt Plates scanned at the Automated Plate Measuring (APM) facility in Cambridge. Low-resolution (≳ 10 Å) spectra were obtained to identify the quasars, primarily at the Las Campanas Observatory. The highest redshift quasar in our survey is at z ≈4.8 ( R =18.7) and its spectrum shows a damped Ly α absorption system at z =4.46. This is currently the highest redshift damped Ly α absorber detected. Five of these quasars exhibit intrinsic broad absorption line features. Combined with the previously published results from the first part of the APM United Kingdom Schmidt Telescope (UKST) survey we have now surveyed a total of ∼8000 deg² of sky i.e. 40 per cent of the high galactic latitude (| b |>30°) sky, resulting in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of which have z ≥4.00.  相似文献   

Emission lines of Na-like ions in spectra obtained with the Solar EUV Research Telescope and Spectrograph (SERTS)     

F. P. Keenan  A. C. Katsiyannis  J. W. Brosius  J. M. Davila  R. J. Thomas 《Monthly notices of the Royal Astronomical Society》2003,342(2):513-518

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The Very Large Telescope Ultraviolet and Visible Echelle Spectrograph survey for molecular hydrogen in high-redshift damped Lyman α systems     

Cédric Ledoux  Patrick Petitjean  R. Srianand 《Monthly notices of the Royal Astronomical Society》2003,346(1):209-228

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