John T. Stocke

University of California, Santa Cruz, Santa Cruz, California, United States

Are you John T. Stocke?

Claim your profile

Publications (341)1014.57 Total impact

  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We report on the observed properties of the plasma revealed through high signal-to-noise (S/N) observations of 54 intervening O VI absorption systems containing 85 O VI and 133 H I components in a blind survey of 14 QSOs observed at ~18 km s-1 resolution with the Cosmic Origins Spectrograph (COS) over a redshift path of 3.52 at z < 0.5. Simple systems with one or two H I components and one O VI component comprise 50% of the systems. For a sample of 45 well-aligned absorption components where the temperature can be estimated, we find evidence for cool photoionized gas in 31 (69%) and warm gas (6 > log T > 5) in 14 (31%) of the components. The total hydrogen content of the 14 warm components can be estimated from the temperature and the measured value of log N(H I). The very large implied values of log N(H) range from 18.38 to 20.38 with a median of 19.35. The metallicity, [O/H], in the 6 warm components with log T > 5.45 ranges from -1.93 to 0.03 with a median value of -1.0 dex. Ground-based galaxy redshift studies reveal that most of the absorbers we detect sample gas in the IGM extending 200 to 600 kpc beyond the closest associated galaxy. We estimate the warm aligned O VI absorbers contain (4.1+/-1.1)% of the baryons at low z. The warm plasma traced by the aligned O VI and H I absorption contains nearly as many baryons as are found in galaxies.
    03/2014;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We use high-quality, medium-resolution HST/COS observations of 75 UV-bright AGN at redshifts $z_{\rm AGN}< 0.85$ to construct the largest survey of the low-redshift IGM to date. The catalog is comprised of 4369 individual extragalactic absorption lines of HI and 20 different metal ions grouped together into 2508 distinct redshift systems at $z_{\rm abs}<0.75$ and represents a significant improvement in total redshift pathlength and weak line sensitivity over previous studies. The column-density distribution of HI systems is seen to evolve both in amplitude and slope at $z< 0.47$. We observe 985 metal lines in 354 systems, and find that the fraction of absorbers detected in metals is strongly dependent on HI column density. OVI absorbers appear to evolve in the same sense as the Ly$\alpha$ forest. A velocity-space two-point correlation function shows substantial clustering of HI absorbers on scales of $\Delta v=50-300\rm~km~s^{-1}$ with no significant clustering at larger $\Delta v$. Most of the clustering signal comes from the stronger ($N_{\rm HI}>10^{13.5}~\rm cm^{-2}$) absorbers particularly those with metal absorption. The full catalog of absorption lines and fully-reduced spectra is available via MAST as a high-level science product at http://archive.stsci.edu/prepds/igm/.
    02/2014;
  • [show abstract] [hide abstract]
    ABSTRACT: We have detected and characterized the circumgalactic medium (CGM) of nearby late-type galaxies using both targeted and serendipitous QSO/galaxy pairs at z < 0.2. Photoionization modeling of warm CGM clouds finds volume filling factors of ~5%, cloud sizes of 0.1-30 kpc, cloud masses of 10-108 M⊙, and metallicities of ~0.1-1 Z⊙. The total mass of these warm clouds surrounding L > 0.1 L* galaxies approaches 1010 M⊙, comparable to the total baryons in massive galaxy disks. We also find evidence for an extensive (>500 kpc), hot (105 - 106 K) intracloud medium that is very massive (> 1011 M⊙). We interpret this hot, massive baryon reservoir as the intragroup medium of spiral-rich galaxy groups and find that its inclusion can solve the missing baryon problem in spiral galaxies.
    01/2014;
  • [show abstract] [hide abstract]
    ABSTRACT: The standard model for propagation of gamma rays from very high energy (VHE, E>100 GeV) blazars through the universe requires an understanding of the diffuse extragalactic background light (EBL). Due to photon-photon collision and pair production from gamma ray/infrared photon interaction in the intergalactic medium, we expect to see a redshift “horizon” beyond which gamma rays from these sources are no longer observable. Three TeV-bright blazars examined in this project pose a problem to the horizon hypothesis due to their substantial redshifts, requiring reevaluation of either the gamma-ray propagation model or the EBL model. This project establishes a minimum density of infrared photons and a potential lower limit on the EBL flux toward these high-z blazars by integrating and summing flux contributions from intervening galaxies within reasonable impact parameters of the blazar sight lines. Galaxies along the lines of sight and their flux contributions are inferred from from measured HI (Lyman alpha forest) and metal-ion absorbers seen in far-UV spectra of PKS1424+240 and 3C66A (HST/COS) and 3C279 (HST/FOS).
    01/2014;
  • [show abstract] [hide abstract]
    ABSTRACT: We present the methodology for ``blind'' millimetre-wave surveys for redshifted molecular absorption in the CO/HCO$^+$ rotational lines. The frequency range $30-50$ GHz appears optimal for such surveys, providing sensitivity to absorbers at $z \gtrsim 0.85$. It is critical that the survey is ``blind'', i.e. based on a radio-selected sample, including sources without known redshifts. We also report results from the first large survey of this kind, using the Q-band receiver on the Green Bank Telescope (GBT) to search for molecular absorption towards 36 sources, 3 without known redshifts, over the frequency range $39.6 - 49.5$ GHz. The GBT survey has a total redshift path of $\Delta z \approx 24$, mostly at $0.81 < z < 1.91$, and a sensitivity sufficient to detect equivalent ${\rm H_2}$ column densities $\gtrsim 3 \times 10^{21}$ cm$^{-2}$ in absorption at $5\sigma$ significance (using the CO-to-${\rm H_2}$ and HCO$^+$-to-${\rm H_2}$ conversion factors of the Milky Way). The survey yielded no confirmed detections of molecular absorption, yielding the $2\sigma$ upper limit $n(z=1.2) < 0.15$ on the redshift number density of molecular gas at column densities $N({\rm H_2}) \gtrsim 3 \times 10^{21}$ cm$^{-2}$.
    12/2013; 782(1).
  • [show abstract] [hide abstract]
    ABSTRACT: The unprecedented far-UV throughput of the Cosmic Origins Spectrograph (COS) is revolutionizing studies of the local intergalactic medium (IGM). In particular, COS is allowing us to refine estimates of the baryon content and metallicity of the IGM, as well as the relationship of IGM absorbers to galaxies. For the past several years we have been using WIYN/HYDRA to obtain spectra of all galaxies brighter than g=20 that are within 20 arcminutes of the ~25 AGN targeted by the COS Science Team that are accessible from the northern hemisphere. When combined with the COS spectra of these AGN, this galaxy redshift survey is enhancing our understanding of the composition and topology of the nearby Universe in both gas and galaxies, allowing us to assess the extent of metal transport away from galaxies, the filling factor of gas and metal-enriched gas in galaxy filaments, and the metallicity of gas in galaxy voids. Here we present estimates of the completeness of our survey along these sight lines and examples of close galaxy-absorber associations discovered by our survey.
    06/2013;
  • [show abstract] [hide abstract]
    ABSTRACT: We present the redshift lower limit of z>0.6035 for the very-high-energy (VHE; E>100 GeV) emitting blazar PKS 1424+240 (PG 1424+240). This limit is inferred from Lyman beta and gamma absorption observed in the far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph. No VHE-detected blazar has shown solid spectroscopic evidence of being more distant. At this distance, VHE observations by VERITAS are shown to sample historically large gamma-ray opacity values at 500 GeV, extending beyond tau=4 for low-level models of the extragalactic background light (EBL) and beyond tau=5 for high-levels. The majority of the z=0.6035 absorption-corrected VHE spectrum appears to exhibit a lower flux than an extrapolation of the contemporaneous LAT power-law fit beyond 100 GeV. However, the highest energy VERITAS point is the only point showing agreement with this extrapolation, possibly implying the overestimation of the gamma-ray opacity or the onset of an unexpected VHE spectral feature. A curved log parabola is favored when fitting the full range of gamma-ray data (0.5 to 500 GeV). While fitting the absorption-corrected VHE data alone results in a harder differential power law than that from the full range, the indices derived using three EBL models are consistent with the physically motivated limit set by Fermi acceleration processes.
    The Astrophysical Journal Letters 04/2013; 768(2). · 6.35 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We have used the Cosmic Origins Spectrograph (COS) to obtain far-UV spectra of three closely-spaced QSO sight lines that probe the circumgalactic medium (CGM) of an edge-on spiral galaxy, ESO 157-49, at impact parameters of 74 and 93 kpc near its major axis and 172 kpc along its minor axis. H I Ly\alpha\ absorption is detected at the galaxy redshift in the spectra of all three QSOs, and metal lines of Si III, Si IV, and C IV are detected along the two major-axis sight lines. Photoionization models of these clouds suggest metallicities close to the galaxy metallicity, cloud sizes of ~1 kpc, and gas masses of ~10^4 solar masses. Given the high covering factor of these clouds, ESO 157-49 could harbor ~2x10^9 solar masses of warm CGM gas. We detect no metals in the sight line that probes the galaxy along its minor axis, but gas at the galaxy metallicity would not have detectable metal absorption with ionization conditions similar to the major-axis clouds. The kinematics of the major-axis clouds favor these being portions of a "galactic fountain" of recycled gas, while two of the three minor-axis clouds are constrained geometrically to be outflowing gas. In addition, one of our QSO sight lines probes a second more distant spiral, ESO 157-50, along its major axis at an impact parameter of 88 kpc. Strong H I Ly\alpha\ and C IV absorption only are detected in the QSO spectrum at the redshift of ESO 157-50.
    The Astrophysical Journal 01/2013; 765(1). · 6.73 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: In three years of science operations onboard HST, the Cosmic OriginsSpectrograph has generated an archive of far-ultraviolet AGN spectra of unprecedented breadth, depth, and quality. COS was designed to be sensitive to many important diagnostic lines in the far-UV (1135-1800A) in the low-redshift, "local" universe: Lya (z<0.47), Lyb (0.1<z<0.7), OVI (0.1<z<0.7), SiIII (z<0.5), CIV (z<0.17), NeVIII (0.45<z<1.3), etc. We report on our ongoing survey of extragalactic absorption systems toward ~200 low- to moderate-redshift (z<1.5), UV-bright AGN. When complete mid-2013), the COS IGM absorber catalog will provide an unbiased, statistical sampling of local intergalactic absorption along ~200 extragalactic sight lines. This significant cornerstone of the scientific legacy of COS is at least an order-of-magnitude improvement over previous low-z IGM surveys in total observed pathlength and number of absorbers as well as substantial improvements in sensitivity and uniformity. Of particular interest is the sensitivity of COS to weak and broad absorption. We discuss the scope of and methodology behind the catalog, several initial discoveries, and the overall statistical findings of the survey. Finally, we discuss the new areas of cosmology enabled by this expanded study.
    01/2013;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The Circumgalactic Medium (CGM) of late-type galaxies is characterized using UV spectroscopy of 11 targeted QSO/galaxy pairs at z < 0.02 with the Hubble Space Telescope Cosmic Origins Spectrograph and ~60 serendipitous absorber/galaxy pairs at z < 0.2 with the Space Telescope Imaging Spectrograph. CGM warm cloud properties are derived, including volume filling factors of 3-5%, cloud sizes of 0.1-30 kpc, masses of 10-1e8 solar masses and metallicities of 0.1-1 times solar. Almost all warm CGM clouds within 0.5 virial radii are metal-bearing and many have velocities consistent with being bound, "galactic fountain" clouds. For galaxies with L > 0.1 L*, the total mass in these warm CGM clouds approaches 1e10 solar masses, ~10-15% of the total baryons in massive spirals and comparable to the baryons in their parent galaxy disks. This leaves >50% of massive spiral-galaxy baryons "missing". Dwarfs (<0.1 L*) have smaller area covering factors and warm CGM masses (<5% baryon fraction), suggesting that many of their warm clouds escape. Constant warm cloud internal pressures as a function of impact parameter ($P/k ~ 10 cm^{-3} K) support the inference that previous COS detections of broad, shallow O VI and Ly-alpha absorptions are of an extensive (~400-600 kpc), hot (T ~ 1e6 K) intra-cloud gas which is very massive (>1e11 solar masses). While the warm CGM clouds cannot account for all the "missing baryons" in spirals, the hot intra-group gas can, and could account for ~20% of the cosmic baryon census at z ~ 0 if this hot gas is ubiquitous among spiral groups.
    The Astrophysical Journal 12/2012; 763(2). · 6.73 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. At present, little observational or theoretical basis exists for understanding the ultraviolet spectra of M dwarfs, despite their critical importance to predicting and interpreting the spectra of potentially habitable planets as they are obtained in the coming decades. Using observations from the Hubble Space Telescope, we present a study of the UV radiation fields around nearby M dwarf planet hosts that covers both FUV and NUV wavelengths. The combined FUV+NUV spectra are publically available in machine-readable format. We find that all six exoplanet host stars in our sample (GJ 581, GJ 876, GJ 436, GJ 832, GJ 667C, and GJ 1214) exhibit some level of chromospheric and transition region UV emission. No "UV quiet" M dwarfs are observed. The bright stellar Ly-alpha emission lines are reconstructed, and we find that the Ly-alpha line fluxes comprise ~37-75% of the total 1150-3100A flux from most M dwarfs; > 10^{3} times the solar value. The F(FUV)/F(NUV) flux ratio, a driver for abiotic production of the suggested biomarkers O2 and O3, is shown to be ~0.5-3 for all M dwarfs in our sample, > 10^{3} times the solar ratio. For the four stars with moderate signal-to-noise COS time-resolved spectra, we find UV emission line variability with amplitudes of 50-500% on 10^{2} - 10^{3} s timescales. Finally, we observe relatively bright H2 fluorescent emission from four of the M dwarf exoplanetary systems (GJ 581, GJ 876, GJ 436, and GJ 832). Additional modeling work is needed to differentiate between a stellar photospheric or possible exoplanetary origin for the hot (T(H2) \approx 2000-4000 K) molecular gas observed in these objects.
    The Astrophysical Journal 12/2012; 763(2). · 6.73 Impact Factor
  • Source
    Ting Yan, John T. Stocke, Jeremy Darling, Fred Hearty
    [show abstract] [hide abstract]
    ABSTRACT: In order to find more examples of the elusive high-redshift molecular absorbers, we have embarked on a systematic discovery program for highly obscured, radio-loud 'invisible active galactic nuclei' using the Very Large Array Faint Images of the Radio Sky at Twenty centimeters radio survey in conjunction with the Sloan Digital Sky Survey (SDSS) to identify 82 strong ({>=}300 mJy) radio sources positionally coincident with late-type, presumably gas-rich galaxies. In this first paper, the basic properties of this sample are described including the selection process and the analysis of the spectral energy distributions (SEDs) derived from the optical (SDSS) + near-IR (NIR) photometry obtained by us at the Apache Point Observatory 3.5 m. The NIR images confirm the late-type galaxy morphologies found by SDSS for these sources in all but a few (6 of 70) cases (12 previously well studied or misclassified sources were culled). Among 70 sources in the final sample, 33 show galaxy type SEDs, 17 have galaxy components to their SEDs, and 20 have quasar power-law continua. At least nine sources with galaxy SEDs have K-band flux densities too faint to be giant ellipticals if placed at their photometric redshifts. Photometric redshifts for this sample are analyzed and found to be too inaccurate for an efficient radio-frequency absorption line search; spectroscopic redshifts are required. A few new spectroscopic redshifts for these sources are presented here but more will be needed to make significant progress in this field. Subsequent papers will describe the radio continuum properties of the sample and the search for redshifted H I 21 cm absorption.
    The Astronomical Journal 10/2012; 144(4). · 4.97 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: There is unique and groundbreaking science to be done with a new generation of UV spectrographs that cover wavelengths in the "Lyman Ultraviolet" (LUV; 912 - 1216 Ang). There is no astrophysical basis for truncating spectroscopic wavelength coverage anywhere between the atmospheric cutoff (3100 Ang) and the Lyman limit (912 Ang); the usual reasons this happens are all technical. The unique science available in the LUV includes critical problems in astrophysics ranging from the habitability of exoplanets to the reionization of the IGM. Crucially, the local Universe (z <= 0.1) is entirely closed to many key physical diagnostics without access to the LUV. These compelling scientific problems require overcoming these technical barriers so that future UV spectrographs can extend coverage to the Lyman limit at 912 Ang.
    09/2012;
  • Source
    T. Yan, J. T. Stocke, J. Darling, F. Hearty
    [show abstract] [hide abstract]
    ABSTRACT: In order to find more examples of the elusive high-redshift molecular absorbers, we have embarked on a systematic discovery program for highly obscured, radio-loud "invisible AGN" using the VLA Faint Images of the Radio Sky at Twenty centimeters (FIRST) radio survey in conjunction with Sloan Digital Sky Survey (SDSS) to identify 82 strong (> 300 mJy) radio sources positionally coincident with late-type, presumably gas-rich galaxies. In this first paper, the basic properties of this sample are described including the selection process and the analysis of the spectral-energydistributions (SEDs) derived from the optical (SDSS) + near-IR (NIR) photometry obtained by us at the Apache Point Observatory 3.5m. The NIR images confirm the late-type galaxy morphologies found by SDSS for these sources in all but a few (6 of 70) cases (12 previously well-studied or misclassified sources were culled). Among 70 sources in the final sample, 33 show galaxy type SEDs, 17 have galaxy components to their SEDs, and 20 have quasar power-law continua. At least 9 sources with galaxy SEDs have K-band flux densities too faint to be giant ellipticals if placed at their photometric redshifts. Photometric redshifts for this sample are analyzed and found to be too inaccurate for an efficient radio-frequency absorption line search; spectroscopic redshifts are required. A few new spectroscopic redshifts for these sources are presented here but more will be needed to make significant progress in this field. Subsequent papers will describe the radio continuum properties of the sample and the search for redshifted H I 21 cm absorption.
    08/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We present empirical scaling relations for the significance of absorption features detected in medium resolution, far-UV spectra obtained with the Cosmic Origins Spectrograph (COS). These relations properly account for both the extended wings of the COS line spread function and the non-Poissonian noise properties of the data, which we characterize for the first time, and predict limiting equivalent widths that deviate from the empirical behavior by \leq 5% when the wavelength and Doppler parameter are in the ranges \lambda = 1150-1750 A and b > 10 km/s. We have tested a number of coaddition algorithms and find the noise properties of individual exposures to be closer to the Poissonian ideal than coadded data in all cases. For unresolved absorption lines, limiting equivalent widths for coadded data are 6% larger than limiting equivalent widths derived from individual exposures with the same signal-to-noise. This ratio scales with b-value for resolved absorption lines, with coadded data having a limiting equivalent width that is 25% larger than individual exposures when b \approx 150 km/s.
    Publications of the Astronomical Society of the Pacific 06/2012; · 3.69 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Ultraviolet observations of the QSO 3C 263 (zem = 0.652) with COS and FUSE reveal O VI absorption systems at z = 0.06342 and 0.14072 . WIYN multi-object spectrograph observations provide information about the galaxies associated with the absorbers. The multi-phase system at z = 0.06342 traces cool photoionized gas and warm collisionally ionized gas associated with a L ~ 0.31L* compact spiral emission line galaxy with an impact parameter of 63 kpc. The cool photoionized gas in the absorber is well modeled with log U ~ -2.6, log N(H) ~17.8, log n(H) ~ -3.3 and [Si/H] = -0.14\pm0.23. The collisionally ionized gas containing C IV and O VI probably arises in cooling shock heated transition temperature gas with log T ~ 5.5. The absorber is likely tracing circumgalactic gas enriched by gas ejected from the spiral emission line galaxy. The simple system at z = 0.14072 only contains O VI and broad and narrow H I. The O VI with b = 33.4\pm11.9 km s-1 is likely associated with the broad H I {\lambda}1215 absorption with b = 86.7\pm15.4 km s-1. The difference in Doppler parameters implies the detection of a very large column of warm gas with log T = 5.61(+0.16, -0.25), log N(H) = 19.54(+0.26, -0.44) and [O/H] = -1.48 (+0.46, -0.26). This absorber is possibly associated with a 1.6L* absorption line galaxy with an impact parameter of 617 kpc although an origin in warm filament gas or in the halo of a fainter galaxy is more likely.
    The Astrophysical Journal 05/2012; 753(1). · 6.73 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Measuring the star formation rate (SFR) at high redshift is crucial for understanding cosmic reionization and galaxy formation. Two common complementary approaches are Lyman-Break-Galaxy (LBG) surveys for large samples and Gamma-Ray-Burst (GRB) observations for sensitivity to SFR in small galaxies. The z>4 GRB-inferred SFR is higher than the LBG rate, but this difference is difficult to understand, as both methods rely on several modeling assumptions. Using a physically motivated galaxy luminosity function model, with star formation in dark-matter halos with virial temperature Tvir>2e4 K (M_DM>2e8 M_sun), we show that GRB and LBG-derived SFRs are consistent if GRBs extend to faint galaxies (M_AB<-11). To test star formation below the detection limit L_lim~0.05L^*_{z=3} of LBG surveys, we propose to measure the fraction f_det(L>L_lim,z) of GRB hosts with L>L_lim. This fraction quantifies the missing star formation fraction in LBG surveys, constraining the mass-suppression scale for galaxy formation, with weak dependence on modeling assumptions. Because f_det(L>L_lim,z) corresponds to the ratio of star formation rates derived from LBG and GRB surveys, if these estimators are unbiased, measuring f_det(L>L_lim,z) also constrains the redshift evolution of the GRB production rate per unit mass of star formation. Our analysis predicts significant success for GRB host detections at z~5 with f_det(L>L_lim,z)~0.4, but rarer detections at z>6. By analyzing the upper limits on host-galaxy luminosities of six z>5 GRBs from literature data, we infer that galaxies with M_AB>-15 were present at z>5 at 95% confidence, demonstrating the key role played by very faint galaxies during reionization.
    The Astrophysical Journal Letters 01/2012; 749(2). · 6.35 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We report deep Green Bank Telescope spectroscopy in the redshifted HI 21cm and OH 18cm lines from the $z = 0.765$ absorption system towards PMN J0134-0931. A comparison between the "satellite" OH 18cm line redshifts, or between the redshifts of the HI 21cm and "main" OH 18cm lines, is sensitive to changes in different combinations of three fundamental constants, the fine structure constant $\alpha$, the proton-electron mass ratio $\mu \equiv m_p/m_e$ and the proton g-factor $g_p$. We find that the satellite OH 18cm lines are not perfectly conjugate, with both different line shapes and stronger 1612 MHz absorption than 1720 MHz emission. This implies that the satellite lines of this absorber are not suitable to probe fundamental constant evolution. A comparison between the redshifts of the HI 21cm and OH 18cm lines, via a multi-Gaussian fit, yields the strong constraint $[\Delta F/F] = [-5.2 \pm 4.3] \times 10^{-6}$, where $F \equiv g_p [\mu \alpha^2]^{1.57}$ and the error budget includes contributions from both statistical and systematic errors. We thus find no evidence for a change in the constants between $z = 0.765$ and the present epoch. Incorporating the constraint $[\Delta \mu/\mu ] < 3.6 \times 10^{-7}$ from another absorber at a similar redshift and assuming that fractional changes in $g_p$ are much smaller than those in $\alpha$, we obtain $[\Delta \alpha/\alpha ] = (-1.7 \pm 1.4) \times 10^{-6}$ over a lookback time of 6.7 Gyrs.
    The Astrophysical Journal Letters 01/2012; 746(2). · 6.35 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: With 20-30 times the throughput of the Hubble Space Telescope's previous far-UV spectrographs at comparable resolution, the Cosmic Origins Spectrograph (COS) is revolutionizing studies of the low-redshift intergalactic medium (IGM). This new wealth of low-redshift IGM absorbers is important because only at the lowest redshifts can we probe the faint end of the galaxy luminosity function to determine the contribution of both dwarf and luminous galaxies to IGM enrichment. We will present results from recent studies of low-redshift galaxy/absorber associations targeted with COS as well as serendipitous associations combed from the STIS archive focusing on the extent and content of a galaxy's circumgalactic medium as a function of its luminosity.
    01/2012;
  • [show abstract] [hide abstract]
    ABSTRACT: Our WIYN/ HYDRA galaxy redshift survey is designed to obtain redshifts for all galaxies with a g-magnitude less than or equal to 20 located within 20’ of 39 different sightlines targeted by the COS GTO team. Data was reduced in IRAF using standard routines and the dohydra task, for spectral extraction. The redshifts were determined by IDL code developed by D. Syphers and were then inspected by eye. The program uses three methods to automatically determine the redshift: cross-correlation using template galaxies, a wavelet search for strong emission lines, and a wavelet search for Ca H&K (and other absorption lines). Inspecting these redshifts required, for each object, a verification of the cross-correlation fit and, depending on the available spectra, a determination of proper emission and absorption features. In conducting our survey of the 3C 263 sightline, we've discovered a number of galaxies in the vicinity of our sightline, including one that happens to be located extremely close to the sightline at the same redshift as an IGM absorber seen in the QSO spectrum. This galaxy's activity may have contributed to our QSO spectrum, allowing us to determine whether or not material may have been ejected from these objects.
    01/2012;

Publication Stats

1k Citations
1,014.57 Total Impact Points

Institutions

  • 2013
    • University of California, Santa Cruz
      • Department of Physics
      Santa Cruz, California, United States
  • 1993–2013
    • University of Colorado
      Denver, Colorado, United States
  • 1986–2013
    • University of Colorado at Boulder
      • • Department of Astrophysical and Planetary Sciences
      • • Center for Astrophysics and Space Astronomy
      Boulder, Colorado, United States
  • 2012
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
  • 2005
    • University of Michigan
      • Department of Astronomy
      Ann Arbor, MI, United States
  • 2001–2004
    • East Tennessee State University
      • Department of Physics and Astronomy
      Johnson City, Tennessee, United States
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
  • 2000
    • Colorado College
      Colorado Springs, Colorado, United States
  • 1992
    • University of Toronto
      Toronto, Ontario, Canada
  • 1985
    • University of North Carolina at Chapel Hill
      North Carolina, United States
  • 1981
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States