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Title: HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C

Abstract

We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21 cm spectra from the Green Bank Telescope. The wide spectral coverage and higher signal-to-noise ratio, compared to previous HST spectra, provide better velocity definition of the HVC absorption, additional ionization species (including high ions), and improved abundances in this halo gas. Complex C has a metallicity of 10%-30% solar and a wide range of ions, suggesting dynamical and thermal interactions with hot gas in the Galactic halo. Spectra in the COS medium-resolution G130M (1133-1468 A) and G160M (1383-1796 A) gratings detect ultraviolet absorption lines from eight elements in low-ionization states (O I, N I, C II, S II, Si II, Al II, Fe II, P II) and three elements in intermediate- and high-ionization states (Si III, Si IV, C IV, N V). Our four active galactic nucleus sight lines toward Mrk 817, Mrk 290, Mrk 876, and PG 1259+593 have high-velocity H I and O VI column densities, log N{sub Hi}= 19.39-20.05 and log N{sub Ovi}= 13.58-14.10, with substantial amounts of kinematically associated photoionized gas. The high-ion abundance ratios are consistentmore » with cooling interfaces between photoionized and collisionally ionized gas: N(C IV)/N(O VI) {approx} 0.3-0.5, N(Si IV)/N(O VI) {approx} 0.05-0.11, N(N V)/N(O VI) {approx} 0.07-0.13, and N(Si IV)/N(Si III) {approx}0.2.« less

Authors:
; ; ;  [1];  [2];  [3]
  1. CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
  2. National Radio Astronomy Observatory, Green Bank, WV 29444 (United States)
  3. Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States)
Publication Date:
OSTI Identifier:
21587454
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 739; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/739/2/105; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; CLOUDS; ELEMENT ABUNDANCE; GALAXIES; GALAXY NUCLEI; PHOTOIONIZATION; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; ABUNDANCE; ELECTROMAGNETIC RADIATION; IONIZATION; RADIATIONS; SORPTION; SPECTRA

Citation Formats

Shull, J. Michael, Stevans, Matthew, Danforth, Charles, Penton, Steven V., Lockman, Felix J., and Arav, Nahum, E-mail: michael.shull@colorado.edu, E-mail: matthew.stevans@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: steven.penton@colorado.edu, E-mail: jlockman@nrao.edu, E-mail: arav@vt.edu. HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C. United States: N. p., 2011. Web. doi:10.1088/0004-637X/739/2/105; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Shull, J. Michael, Stevans, Matthew, Danforth, Charles, Penton, Steven V., Lockman, Felix J., & Arav, Nahum, E-mail: michael.shull@colorado.edu, E-mail: matthew.stevans@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: steven.penton@colorado.edu, E-mail: jlockman@nrao.edu, E-mail: arav@vt.edu. HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C. United States. doi:10.1088/0004-637X/739/2/105; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Shull, J. Michael, Stevans, Matthew, Danforth, Charles, Penton, Steven V., Lockman, Felix J., and Arav, Nahum, E-mail: michael.shull@colorado.edu, E-mail: matthew.stevans@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: steven.penton@colorado.edu, E-mail: jlockman@nrao.edu, E-mail: arav@vt.edu. Sat . "HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C". United States. doi:10.1088/0004-637X/739/2/105; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21587454,
title = {HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C},
author = {Shull, J. Michael and Stevans, Matthew and Danforth, Charles and Penton, Steven V. and Lockman, Felix J. and Arav, Nahum, E-mail: michael.shull@colorado.edu, E-mail: matthew.stevans@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: steven.penton@colorado.edu, E-mail: jlockman@nrao.edu, E-mail: arav@vt.edu},
abstractNote = {We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21 cm spectra from the Green Bank Telescope. The wide spectral coverage and higher signal-to-noise ratio, compared to previous HST spectra, provide better velocity definition of the HVC absorption, additional ionization species (including high ions), and improved abundances in this halo gas. Complex C has a metallicity of 10%-30% solar and a wide range of ions, suggesting dynamical and thermal interactions with hot gas in the Galactic halo. Spectra in the COS medium-resolution G130M (1133-1468 A) and G160M (1383-1796 A) gratings detect ultraviolet absorption lines from eight elements in low-ionization states (O I, N I, C II, S II, Si II, Al II, Fe II, P II) and three elements in intermediate- and high-ionization states (Si III, Si IV, C IV, N V). Our four active galactic nucleus sight lines toward Mrk 817, Mrk 290, Mrk 876, and PG 1259+593 have high-velocity H I and O VI column densities, log N{sub Hi}= 19.39-20.05 and log N{sub Ovi}= 13.58-14.10, with substantial amounts of kinematically associated photoionized gas. The high-ion abundance ratios are consistent with cooling interfaces between photoionized and collisionally ionized gas: N(C IV)/N(O VI) {approx} 0.3-0.5, N(Si IV)/N(O VI) {approx} 0.05-0.11, N(N V)/N(O VI) {approx} 0.07-0.13, and N(Si IV)/N(Si III) {approx}0.2.},
doi = {10.1088/0004-637X/739/2/105; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 739,
place = {United States},
year = {2011},
month = {10}
}