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Register a new userQuasar Absorption Lines in the Far Ultraviolet: An Untapped Gold Mine for Galaxy Evolution Studies
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Todd Tripp
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This white paper emphasizes the potential of QSO absorption lines in the rest-frame far/extreme UV at rest-frame wavelengths from ~500 to 2000 A. In this wavelength range, species such as Ne VIII, Na IX, and Mg X can be detected, providing diagnostics of gas with temperatures >> 10^{6} K, as well as banks of adjacent ions such as O I, O II, O III, O IV, O V, and O VI (and similarly N I - N V; S II - S VI; Ne II - Ne VIII, etc.), which constrain physical conditions with unprecedented precision. A UV spectrograph with good sensitivity down to observed wavelengths of 1000 A can detect these new probes in absorption systems with redshift z(abs) > 0.3, and at these redshifts, the detailed relationships between the absorbers and nearby galaxies and large-scale environment can be studied from the ground. By observing QSOs at z = 1.0 - 1.5, HST has started to exploit extreme-UV QSO absorption lines, but HST can only reach a small number of these targets. A future, more sensitive UV spectrograph could open up this new discovery space.
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As one of the most luminous radio-loud quasars showing intrinsic ultraviolet (UV) and X-ray absorption, 3C 351 provides a laboratory for studying the kinematics and physical conditions of such ionized absorbers. We present an analysis of the intrinsic absorption lines in the high-resolution ($sim$ 7 km/s) far-UV spectrum which was obtained from observations with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The spectrum spans wavelengths from 1150 AA to 1710 AA, and shows strong emission lines from O VI and Ly$alpha$. Associated absorption lines are present on the blue wings of the high-ionization emission doublets O VI $lambdalambda$ 1032,1038 and N V $lambdalambda$ 1238,1242, as well as the Lyman lines through Ly$epsilon$. These intrinsic absorption features are resolved into several distinct kinematic components, covering rest-frame velocities from -40 to -2800 km/s, with respect to the systemic redshift of $z_{em}=0.3721$. For the majority of these absorption line regions, strong evidence of partial covering of both the background continuum source and the BELR is found, which supports the intrinsic absorption origin and rules out the possibility that the absorption arises in some associated cluster of galaxies. The relationship between the far-UV absorbers and X-ray `warm absorbers are studied with the assistance of photoionization models. Most of the UV associated absorption components have low values of the ionization parameter and total hydrogen column densities, which is inconsistent with previous claims that the UV and X-ray absorption arises in the same material. Analysis of these components supports a picture with a wide range of ionization parameters, temperatures, and column densities in AGN outflows.
The absorption lines observed in quasar spectra have given us a detailed picture of the intergalactic medium and the metal abundance and kinematics of high redshift galaxies. In this review, we present an introduction to the field, starting with the techniques used for interpreting absorption line spectra. We then survey the observational and theoretical development of our understanding of the Lyman-alpha forest, the metal absorbers, and the damped Ly-alpha absorbers. We conclude with a discussion of some of the remaining outstanding issues, and prospects for the future.
The galaxy database GOLDmine (http://goldmine.mib.infn.it/) has been significantly updated (Sept/1/2003) The new features include: a) Sample extension:the GOLDmine sample has been extended from the original Virgo cluster + Coma supercluster regions to include the clusters: A262, Cancer, A2147, A2151, A2197, A2199. 382 galaxies from the GCGC (with m_p<15.7) have been added in these regions. b) New query keys: 1) query by near position (and near name). 2) query by available images. c) Routinary image update: 1) 59 (B). 72 (V) and 70 (H_alpha) new frames from observations carried on by the GOLDmine team in spring 2003. 2) 157 new optical (drift-scan) spectra from observations carried on by the GOLDmine team in 2002-2003. 3) 225 B frames of VCC galaxies taken with the INT (kindly provided by S. Sabatini). 4) 56 B frames of galaxies in A1367 taken with the CFHT (kindly provided by M. Treyer). 5) 20 (H), 32 (K) band frames of bright Virgo members (from 2MASS). The new numbers in GOLDmine are: 3649 galaxies, 706 V-band frames, 858 B-band frames, 385 H_alpha frames (NET), 385 H_alpha frames (OFF-band), 1241 H-band frames, 114 K-band frames, 323 Spectra All frames are available in FITS (and jpg) format.
We present three Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the Narrow-Line Seyfert 1 galaxy NGC4051. The most prominent features in the far-ultraviolet (FUV) spectrum are the OVI emission and absorption lines and the HI Lyman series absorption lines which are detected up to the Lyman edge. We also identify weak emission from NIII, CIII, and HeII. The CIII line shows absorption while none is detected in the NIII and HeII lines. In HI and CIII we detect two main absorption systems at outflow velocities of -50+/-30 and -240+/-40 km/s, as well as a possible third one at ~ -450 km/s. These systems are consistent in velocity with the 10 absorption systems found previously in CIV, NV, and SiIV, though the individual systems are blended together in the FUV spectrum. We estimate column densities of the two main absorption systems and find that the HI column density is lower for systems with larger outflow velocity. We detect no flux or spectral variations of NGC4051 at FUV wavelengths during three epochs spanning one year. This is consistent with the optical light curve which shows no variations between the three epochs. It is also consistent with the X-ray light curve which shows consistent flux levels at the three epochs of the FUSE observations, although the X-ray light curve shows strong variations on much shorter timescales.
We present the first intermediate-resolution (lambda / 3000) spectrum of the bright quasi-stellar object 3C273 at wavelengths between 900 and 1200 A. Observations were performed with the Berkeley spectrograph aboard the ORFEUS-SPAS II mission. We detect Lyman beta counterparts to previously-identified intergalactic Lyman-alpha features at cz = 19900, 1600, and 1000 km/s; counterparts to other putative Lyman-alpha clouds along the sight line are below our detection limit. The strengths of the two very low redshift Lyman-beta features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations, suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H I column density of 4 E14/cm^2 for the 1600 km/s cloud. We find marginally significant evidence for Galactic H_2 along the sight line, with a total column density of about 1 E15/cm^2. We detect the stronger interstellar O VI doublet member unambiguously; the weaker member is blended with other features. If the Doppler b value for O VI is comparable to that determined for N V then the O VI column density is 7 +/- 2 E14/cm^2, significantly above the only previous estimate. The O VI / N V ratio is about 10, consistent with the low end of the range observed in the disk. Additional interstellar species detected for the first time toward 3C273 (at modest statistical significance) include P II, Fe III, Ar I, and S III.
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