Extraplanar Dust in Spiral Galaxies: Tracing Outflows in the Disk-Halo Interface (2009)
There is now ample evidence that the interstellar thick disks of spiral galaxies are dusty. Although the majority of extraplanar gas in the first few kiloparsecs above the plane of a spiral galaxy is...
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...
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...
The High Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy (2008)
Zech, William F., Lehner, Nicolas, Howk, J. Christopher, Dixon, W. Van Dyke, Brown, Thomas M.
We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS E140M) observations of the post-asymptotic giant branch star ZNG 1 in the globular cluster...
The Ucsd/Keck Damped Lya Abundance Database: A Decade of High Resolution Spectroscopy (2007)
Prochaska, Jason X., Wolfe, Arthur M., Howk, J. Christopher, Gawiser, Eric, Burles, Scott M., Cooke, Jeff
We publish the Keck/HIRES and Keck/ESI spectra that we have obtained during the first 10 years of Keck observatory operations. Our full sample includes 42 HIRES spectra and 39 ESI spectra along 65...
Simulations of Mixed Morphology Supernova Remnants With Anisotropic Thermal Conduction (2006)
Tilley, David A., Balsara, Dinshaw S., Howk, J. Christopher
We explore the role of anisotropic thermal conduction on the evolution of supernova remnants through interstellar media with a range of densities via numerical simulations. We find that a remnant...
The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System (2006)
Jorgenson, Regina A., Wolfe, Arthur M., Prochaska, Jason X., Lu, Limin, Howk, J. Christopher, Cooke, Jeff, ...
As large optical quasar surveys for damped Lya become a reality and the study of star forming gas in the early Universe achieves statistical robustness, it is now vital to identify and quantify the...
Howk, J. Christopher, Sembach, Kenneth R., Savage, Blair D.
We describe a new method for determining total gas-phase abundances for the Galactic ISM with minimal ionization uncertainties. For sight lines toward globular clusters containing both UV-bright...
Evidence for Correlated Titanium and Deuterium Depletion in the Galactic ISM (2005)
Prochaska, Jason X., Tripp, Todd M., Howk, J. Christopher
Current measurements indicate that the deuterium abundance in diffuse interstellar gas varies spatially by a factor of ~4 among sightlines extending beyond the Local Bubble. One plausible explanation...
Elemental Abundances in Two High Column Density Damped Lyman Alpha Systems at z < 1.5 (2004)
Rao, Sandhya M., Prochaska, Jason X., Howk, J. Christopher, Wolfe, Arthur M.
We present Keck/HIRES abundance measurements and metal-line kinematic profiles of the damped Lyman alpha systems (DLAs) towards the quasars Q0933+733 (z_abs=1.479) and Q0948+433 (z_abs=1.233). These...
Prochaska, Jason X., Chen, Hsiao-Wen, Howk, J. Christopher, Weiner, Benjamin J., Mulchaey, John
We present results from an analysis of FUSE and HST/STIS spectroscopy of the z_em=0.57 quasar PKS0405-123. We focus on the intervening metal-line systems identified along the sightline and...
Cold Neutral Gas in a z=4.2 Damped Lyman-alpha System: The Fuel for Star Formation (2004)
Howk, J. Christopher, Wolfe, Arthur M., Prochaska, Jason X.
We discuss interstellar temperature determinations using the excitation equilibrium of the ^2P levels of Si II and C II. We show how observations of the ^2P_3/2 fine structure levels of Si II and C...
Cooling in Coronal Gas in the M82 Starburst Superwind (2003)
Hoopes, Charles G., Heckman, Timothy M., Strickland, David K., Howk, J. Christopher
We have used the Far Ultraviolet Spectroscopic Explorer to search for OVI 1031.926 Angstrom emission at four locations in the starburst superwind of M82. No OVI emission was detected at any of the...
On the Origin of the High-Ionization Intermediate-Velocity Gas Toward HD 14434 (2003)
Knauth, David C., Howk, J. Christopher, Sembach, Kenneth R., Lauroesch, James T., Meyer, David M.
We present Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph observations of high-ionization interstellar absorption toward HD 14434 [(l, b) = (135.1, -3.8); d ~ 2.3...
Oliveira, Cristina M., Hebrard, Guillaume, Howk, J. Christopher, Kruk, Jeffrey W., Chayer, Pierre, Moos, H. Warren
The interstellar abundances of D I, N I, and O I in the local ISM are studied us ing high-resolution spectra of four hot white dwarfs. The spectra of GD 246, WD 2331$-$475, HZ 21, and Lan 23 were...
Ionized Gas in the First 10 kpc of the Interstellar Galactic Halo (2002)
Howk, J. Christopher, Sembach, Kenneth R., Savage, Blair D.
We present FUSE observations of the post-asymptotic giant branch star von Zeipel 1128 (l=42.5, b=+78.7; z=10.0 kpc), located in the globular cluster Messier 3. The FUSE observations cover the...
Origins of the Highly Ionized Gas along the Line of Sight towards HD 116852 (2002)
Fox, Andrew J., Savage, Blair D., Sembach, Kenneth R., Fabian, Dirk, Richter, Philipp, Meyer, David M., ...
We present Hubble Space Telescope Imaging Spectrograph (HST/STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) observations of high ion interstellar absorption along the sight line to HD 116852....
FUSE Observations of Degree-Scale Variations in Galactic Halo O VI (2002)
Howk, J. Christopher, Savage, Blair D., Sembach, Kenneth R., Hoopes, Charles G.
We report Far Ultraviolet Spectroscopic Explorer (FUSE) observations of interstellar O VI absorption in the halo of the Milky Way towards 12 early-type stars in the Large Magellanic Cloud (LMC) and...
Prochaska, Jason X., Howk, J. Christopher, O'Meara, John M., Tytler, David, Wolfe, Arthur M., Kirkman, David, ...
We investigate the ionization state of the damped Lya system at z=2.62 toward GB1759+7539 through an analysis of ionic ratios sensitive to photoionization: ArI/SII, FeIII/FeII, NII/NI, AlIII/AlII....
A FUSE Survey of Interstellar O VI Absorption in the Small Magellanic Cloud (2002)
Hoopes, Charles G., Sembach, Kenneth R., Howk, J. Christopher, Savage, Blair D., Fullerton, Alex W.
We present the results of a FUSE survey of O VI 1031.93 Angstrom and 1037.62 Angstrom absorption toward 18 OB stars in the Small Magellanic Cloud (SMC). We detect O VI along every sight line. The...
Howk, J. Christopher, Sembach, Kenneth R., Savage, Blair D., Massa, Derck, Friedman, Scott D., Fullerton, Alex W.
We present FUSE observations of interstellar O VI absorption towards 12 early-type stars in the Large Magellanic Cloud (LMC). O VI 1031.926 Ang absorption at LMC velocities is seen towards all 12...
An Atlas of FUSE Sight Lines Toward the Magellanic Clouds (2001)
Danforth, Charles W., Howk, J. Christopher, Fullerton, Alex W., Blair, William P., Sembach, Kenneth R.
We present an atlas of 57 Large Magellanic Cloud (LMC) and 37 Small Magellanic Cloud (SMC) observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. The atlas highlights...
Interstellar O VI in the Large Magellanic Cloud (2001)
I summarize Far Ultraviolet Spectroscopic Explorer (FUSE) observations of interstellar O VI absorption towards 12 early-type stars in the Large Magellanic Cloud (LMC), the closest disk galaxy to the...
Hoopes, Charles G., Sembach, Kenneth R., Howk, J. Christopher, Blair, William P.
We report a detection of far ultraviolet absorption from the supernova remnant SNR 0057 - 7226 in the Small Magellanic Cloud (SMC). The absorption is seen in the Far Ultraviolet Spectroscopic...
Ionization Properties and Elemental Abundances in Damped Ly alpha Systems (2001)
Vladilo, Giovanni, Centurion, Miriam, Bonifacio, Piercarlo, Howk, J. Christopher
We analyze extant data of Al++, Al+ and other low ions with the aim of studying the ionization properties of Damped Ly alpha systems (DLAs) from the analysis of the ratio R(Al++/Al+) =...
Sembach, Kenneth. R., Howk, J. Christopher, Savage, Blair. D., Shull, J. Michael
We present Far Ultraviolet Spectroscopic Explorer observations of the atomic and molecular absorption in high velocity cloud HVC 287.5+22.5+240, which lies in front of the ultraviolet-bright nucleus...
Empirical Verification of the Fe II Oscillator Strengths in the FUSE Bandpass (2000)
Howk, J. Christopher, Sembach, Kenneth R., Roth, Katherine C., Kruk, Jeffrey W.
We report empirical determinations of atomic oscillator strengths, or f-values, for 11 ground-state transitions of Fe II in the wavelength range 1050 to 1150 Ang. We use ultraviolet absorption line...
The Abundance of Interstellar Boron (2000)
Howk, J. Christopher, Sembach, Kenneth R., Savage, Blair D.
We use new Space Telescope Imaging Spectrograph (STIS) and archival Goddard High Resolution Spectrograph (GHRS) observations to study interstellar B II 1362 and O I 1355 absorption along seven...
Howk, J. Christopher, Sembach, Kenneth R.
We present a simple, effective approach for estimating the on-order backgrounds of spectra taken with the highest-resolution modes of the Space Telescope Imaging Spectrograph (STIS) on-board the...
Stagnation and Infall of Dense Clumps in the Stellar Wind of tau Scorpii (1999)
Howk, J. Christopher, Cassinelli, Joseph, Bjorkman, Jon, Lamers, Henny
Observations of the B0.2V star tau Scorpii have revealed unusual stellar wind characteristics: red-shifted absorption in the far-ultraviolet O VI resonance doublet up to +250 km/s, and extremely hard...
The Multiphase Halo of NGC 891: WIYN H-alpha and BVI Imaging (1999)
Howk, J. Christopher, Savage, Blair D.
We present new, deep optical images (BVI+H-alpha) of the interstellar medium (ISM) far above the plane of NGC 891. These sub-arcsecond images give a direct visual view of two physically distinct...
Extraplanar Dust in Spiral Galaxies: Observations and Implications (1999)
Recent optical and submillimeter observations have begun to probe the existence of dust grains in the halos of spiral galaxies. I review our own work in this area which employs high-resolution...
Modeling the Warm Ionized Interstellar Medium and Its Impact on Elemental Abundance Studies (1999)
Sembach, Kenneth R., Howk, J. Christopher, Ryans, Robert S. I., Keenan, Francis P.
We present model calculations of ionization fractions for elements in the warm (log T = 4), low-density photoionized interstellar medium (WIM) of the Milky Way. We model the WIM as a combination of...
Ionized Gas in Damped Lyman-alpha Systems and Its Effects on Elemental Abundance Studies (1999)
Howk, J. Christopher, Sembach, Kenneth R.
Recent high-resolution observations of metal absorption lines in high-redshift damped Ly-alpha systems have shown that Al III, a tracer of moderately-ionized gas, very often has a velocity structure...
Abundances and Physical Conditions in the Warm Neutral Medium Towards mu Columbae (1999)
Howk, J. Christopher, Savage, Blair D., Fabian, Dirk
We present ultraviolet interstellar absorption line measurements for the sightline towards the O9.5 V star mu Columbae obtained with the Goddard High Resolution Spectrograph (GHRS) on board the...
A Search for Extraplanar Dust in Nearby Edge-On Spirals (1999)
Howk, J. Christopher, Savage, Blair D.
We present high resolution BV images of 12 edge-on spiral galaxies observed with the WIYN 3.5-m telescope. These images were obtained to search for extraplanar (|z| > 0.4 kpc) absorbing dust...
Extraplanar Dust and Star Formation in Nearby Edge-On Galaxies (1998)
Howk, J. Christopher, Savage, Blair D.
We present high-resolution ( 0.5 - 2.0. If Milky Way gas-to-dust relationships are appropriate, then these structures have gaseous column densities N_H > 10(21) cm(-2), with very large masses (>10(5)...
Dust in the Ionized Medium of the Galaxy: GHRS Measurements of Al III and S III (1998)
Howk, J. Christopher, Savage, Blair D.
We present interstellar absorption line measurements of the ions S III and Al III towards six stars using archival Goddard High Resolution Spectrograph data. The ions Al III and S III trace heavily...
Extraplanar Dust in the Edge-On Spiral NGC 891 (1997)
Howk, J. Christopher, Savage, Blair D.
We present high-resolution (