Quasar Absorption Lines
The spectrum of the quasar Q1425+6039 shown above was obtained with the High Resolution Echelle
Spectrograph (HIRES) on the Keck I Telescope. This instrument has revolutionized the study of
the absorption lines observed in the spectra of quasars. The quasar has an emission redshift of z = 3.18. To the left of the Lyman alpha emission line you see the "forest" of H I absorption lines produced by intervening, tenuous intergalactic clouds. (For a review see M. Rauch "The Lyman Alpha Forest in the
Spectra of QSOs'' .) The particularly strong line at 4650 A
is a "damped Lyman alpha" absorption feature at a redshift of z = 2.82 produced in a cloud which is optically thick in H I. Many of the weak absortion features on the long
wavelength side of the Lyman alpha emission line are low ioization lines of heavier elements (O I, Si II, C II, etc. ) associated with this system. Other features are
C IV and Mg II resonance doublets produced in the halos of intervening galaxies.
Most of what we know about the physics and composition of the intergalactic medium
and the interstellar gas in galaxies has come from analyses of quasar absorption spectra
like the one shown.
I am collaborating on the study of quasar absorption spectra principally with M. Rauch (OCIW), G. Becker (OCIW) and B. Penprase (Pomona College).
The following are some of our recent papers on quasar absorption lines:
- The Evolution of Optical Depth in the Ly-alpha Forest: Evidence Against Reionization at z ~6; Ap. J. 662, 72 (2007) G. Becker, W. Sargent and M. Rauch.
- Discovery of Excess O I Absorption Towards the z = 6.42 QSO SDSS J1148+5251; Ap. J. 640, 69 (2006) G. Becker, W. Sargent, M. Rauch and R. Simcoe.
- Observations of Chemically Enriched QSO Absorbers near z ~ 2.3 Galaxies:
Star-Formation Feedback Signatures in the IGM; Ap. J., 637, 648 (2006) , R. Simcoe, W. L. W. Sargent, M. Rauch and G. Becker.
- Expansion and Collapse in the Cosmic Web; Ap. J. 632, 58 (2005)
M. Rauch, G. Becker, M. Viel, W. L. W. Sargent, A. Smette, R. Simcoe, T. Barlow,
and M. Haehnelt.
- Large-Scale Correlations in the Ly-alpha Forest at z = 3.4; Ap. J.
613, 61 (2004) , G. D. Becker, W. L. W. Sargent and M. Rauch.
- The Distribution of Metallicity in the IGM at z ~ 2.5: O VI and C IV
Absorption in the Spectra of 7 QSOs; Ap. J.; 606, 92 (2004),
R. A. Simcoe, W. L. W. Sargent and M. Rauch.
- The Prompt Inventory from Very Massive Stars and Elemental Abundances
in Ly-alpha Systems; Ap. J. Letters, 569, L61 (2002) , Y.-Z. Qian,
W. L. W. Sargent, and G. J. Wasserburg.
- Characterizing the Warm-Hot IGM at High Redshift: A High Resolution Survey
for OVI at z = 2.5; Ap. J., 578, 737 (2002) , R. A. Simcoe,
W. L. W. Sargent, and M. Rauch.
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page by Wallace Sargent, last updated 13 March 2008