J. Xavier Prochaska

MASE: A New Data--Reduction Pipeline for the Magellan Echellette Spectrograph (2009)

Bochanski, John J., Hennawi, Joseph F., Simcoe, Robert A., Prochaska, J. Xavier, West, Andrew A., Burgasser, Adam J., ...

We introduce a data reduction package written in Interactive Data Language (IDL) for the Magellan Echellete Spectrograph (MAGE). MAGE is a medium-resolution (R ~4100), cross-dispersed, optical...

A Direct Measurement of the IGM Opacity to HI Ionizing Photons (2009)

Prochaska, J. Xavier, Worseck, Gabor, O'Meara, John M.

We present a new method to directly measure the opacity from HI Lyman limit (LL) absorption k_LL along quasar sightlines by the intergalactic medium (IGM). The approach analyzes the average...

Direct Evidence of Cold Gas in DLA 0812+32B (2009)

Jorgenson, Regina A., Wolfe, Arthur M., Prochaska, J. Xavier, Carswell, Robert F.

We present the first direct evidence for cold gas in a high redshift DLA galaxy. We measured several multiplets of weak neutral carbon (CI) transitions in order to perform a curve of growth analysis....

An Observational Determination of the Proton to Electron Mass Ratio in the Early Universe (2009)

Thompson, Rodger I., Bechtold, Jill, Black, John H., Eisenstein, Daniel, Fan, Xiaohui, Kennicutt, Robert C., ...

In an effort to resolve the discrepancy between two measurements of the fundamental constant mu, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in...

GRB 090426: The Environment of a Rest-Frame 0.35-second Gamma-Ray Burst at Redshift z=2.609 (2009)

Levesque, Emily M., Bloom, Joshua S., Butler, Nathaniel R., Perley, Daniel A., Cenko, S. Bradley, Prochaska, J. Xavier, ...

We present the discovery of an absorption-line redshift of z = 2.609 for GRB 090426, establishing the first firm lower limit to a redshift for a gamma-ray burst with an observed duration of 90%...

A Survey of UV Bright Sources Behind the Halo of M31 (2009)

Fittingoff, Andrew, Prochaska, J. Xavier, Kalirai, Jasonjot S., Strader, Jay, Guhathakurta, Puragra, Kaplan, Kyle F.

We have performed a wide-area ultraviolet (UV) imaging survey using the GALaxy Evolution eXplorer (GALEX) to search for bright, point-like UV sources behind M31's extended halo. Our survey consisted...

Galaxies probing galaxies: cool halo gas from a z = 0.47 post-starburst galaxy (2009)

Rubin, Kate H. R., Prochaska, J. Xavier, Koo, David C., Phillips, Andrew C., Weiner, Benjamin J.

We study the cool gas around a galaxy at z = 0.4729 using Keck/LRIS spectroscopy of a bright (B = 21.7) background galaxy at z = 0.6942 at a transverse distance of 16.5/h_70 kpc. The background...

The Last Eight-Billion Years of Intergalactic CIV Evolution (2009)

Cooksey, Kathy L., Thom, Christopher, Prochaska, J. Xavier, Chen, Hsiao-Wen

We surveyed the HST UV spectra of 49 low-redshift quasars for z < 1 CIV candidates, relying solely on the characteristic wavelength separation of the doublet. After consideration of the defining...

On the Absence of High Metallicity-High Column Density Damped Lyman Alpha Systems: Molecule Formation in a Two-Phase Interstellar Medium (2009)

Krumholz, Mark R., Ellison, Sara L., Prochaska, J. Xavier, Tumlinson, Jason

We argue that the lack of observed damped Lyman alpha (DLA) systems that simultaneously have high HI columns densities and high metallicities results naturally from the formation of molecules in the...

Casting light on the 'anomalous' statistics of Mg II absorbers toward Gamma-Ray Burst afterglows: the incidence of weak systems (2009)

Tejos, Nicolas, Lopez, Sebastian, Prochaska, J. Xavier, Bloom, Joshua S., Chen, Hsiao-Wen, Dessauges-Zavadsky, Miroslava, ...

We revisit echelle spectra (spectral resolution R ~ 40000) of 8 Gamma-Ray Burst afterglows to obtain the incidence (dN/dz) of weak intervening Mg II systems at a mean redshift of = 1.5. We show that...

The Synoptic All-Sky Infrared (SASIR) Survey (2009)

Bloom, Joshua S., Prochaska, J. Xavier, Lee, William, González, J. Jesús, Ramírez-Ruiz, Enrico, Bolte, Michael, ...

We are proposing to conduct a multicolor, synoptic infrared (IR) imaging survey of the Northern sky with a new, dedicated 6.5-meter telescope at San Pedro M\'artir (SPM) Observatory. This initiative...

Metal-Enriched Plasma in Protogalactic Halos: A Survey of N V Absorption in High-z Damped & Sub-Damped Lyman-alpha Systems (2009)

Fox, Andrew J., Prochaska, J. Xavier, Ledoux, Cédric, Petitjean, Patrick, Wolfe, Arthur M., Srianand, Raghunathan

We continue our recent work to characterize the plasma content of high-redshift damped and sub-damped Lyman-alpha systems (DLAs/sub-DLAs), which represent multi-phase gaseous (proto)galactic disks...

Wavelength Accuracy of the Keck HIRES Spectrograph and Measuring Changes in the Fine Structure Constant (2009)

Griest, Kim, Whitmore, Jonathan B., Wolfe, Arthur M., Prochaska, J. Xavier, Howk, J. Christopher, Marcy, Geoffrey W.

We report on an attempt to accurately wavelength calibrate four nights of data taken with the Keck HIRES spectrograph on QSO PHL957, for the purpose of determining whether the fine structure constant...

Molecular hydrogen deficiency in HI-poor galaxies and its implications for star formation (2009)

Fumagalli, Michele, Krumholz, Mark R., Prochaska, J. Xavier, Gavazzi, Giuseppe, Boselli, Alessandro

We use a sample of 47 homogeneous and high sensitivity CO images taken from the Nobeyama and BIMA surveys to demonstrate that, contrary to common belief, a significant number (~40%) of HI-deficient...

Strong z~0.5 O VI Absorption Toward PKS 0405-123: Implications for Ionization and Metallicity of the Cosmic Web (2009)

Howk, J. Christopher, Ribaudo, Joseph S., Lehner, Nicolas, Prochaska, J. Xavier, Chen, Hsiao-Wen

We present observations of the O VI system at z_abs = 0.495096 toward PKS 0405-123 (z_em = 0.5726) obtained with FUSE and STIS. In addition to strong O VI, with log N(O VI) = 14.47+/-0.02, and...

On the (Non)Evolution of HI Disks over Cosmic Time (2008)

Prochaska, J. Xavier, Wolfe, Arthur M.

We present new results on the frequency distribution of projected HI column densities f(N,X), total comoving covering fraction, and integrated mass densities rho_HI of high redshift, HI `disks' from...

A z = 3 Lyman Alpha Blob Associated with a Damped Lyman Alpha System Proximate to its Background Quasar (2008)

Hennawi, Joseph F., Prochaska, J. Xavier, Kollmeier, Juna, Zheng, Zheng

We report on the discovery of a bright Lyman alpha blob associated with the z=3 quasar SDSSJ124020.91+145535.6 which is also coincident with strong damped Lyman alpha absorption from a foreground...

Quasars Probing Quasars III: New Clues to Feedback, Quenching, and the Physics of Massive Galaxy Formation (2008)

Prochaska, J. Xavier, Hennawi, Joseph F.

Galaxies hosting z~2 quasars are the high-$z$ progenitors of today's massive `red-and-dead' galaxies. With close pairs of quasars at different redshifts, a background quasar can be used to study a...

Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3 (2008)

Fynbo, Johan P. U., Prochaska, J. Xavier, Sommer-Larsen, Jesper, Dessauges-Zavadsky, Miroslava, Moller, Palle

We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-alpha (DLA) systems are drawn from the population of UV-selected...