DISTRIBUTION OF FAINT ATOMIC GAS IN HICKSON COMPACT GROUPS

Journal Article · Sat Oct 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/812/1/78· OSTI ID:22525272

Borthakur, Sanchayeeta; Heckman, Timothy M.; Zhu, Guangtun ^[1]; Yun, Min Su ^[2]; Verdes-Montenegro, Lourdes ^[3]

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1. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
2. Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
3. Instituto de Astrofísica de Andalucía, CSIC, Apdo. Correos 3004, E-18080 Granada (Spain)

We present 21 cm H i observations of four Hickson Compact Groups (HCGs) with evidence for a substantial intragroup medium using the Robert C. Byrd Green Bank Telescope (GBT). By mapping H i emission in a region of 25′ × 25′ (140–650 kpc) surrounding each HCG, these observations provide better estimates of H i masses. In particular, we detected 65% more H i than that detected in the Karl G. Jansky Very Large Array (VLA) imaging of HCG 92. We also identify whether the diffuse gas has the same spatial distribution as the high surface brightness (HSB) H i features detected in the VLA maps of these groups by comparing the H i strengths between the observed and modeled masses based on VLA maps. We found that the H i observed with the GBT has a similar spatial distribution to the HSB structures in HCG 31 and HCG 68. Conversely, the observed H i distributions in HCG 44 and HCG 92 were extended and showed significant offsets from the modeled masses. Most of the faint gas in HCG 44 lies to the northeast–southwest region and in HCG 92 lies in the northwest region of their respective groups. The spatial and dynamical similarities between the total (faint+HSB) and the HSB H i indicate that the faint gas is of tidal origin. We found that the gas will survive ionization by the cosmic UV background and the escaping ionizing photons from the star-forming regions and stay primarily neutral for at least 500 Myr.

• OSTI ID: 22525272
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 812; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
COMPARATIVE EVALUATIONS
COSMIC PHOTONS
GALAXIES
HYDROGEN IONS
IONIZATION
MAPPING
MASS
SPATIAL DISTRIBUTION
STAR EVOLUTION
STARS
SURFACES
TELESCOPES