Deep Chandra Observations of HCG 16 - I. Active Nuclei, Star formation and Galactic Winds

Abstract

We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610~MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation and the high luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe-K$\alpha$ emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infra-red and ultra-violet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

18 pages, 11 figures, 11 tables, accepted for publication in ApJ; updated references and fixed typos identified at proof stage

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Cited by in corpus (8)

• A Review of Recent Observations of Galactic Winds Driven by Star Formation
• A hard X-ray view of Luminous and Ultra-luminous Infrared Galaxies in GOALS: I - AGN obscuration along the merger sequence
• Comprehensive Broadband X-ray and Multiwavelength Study of Active Galactic Nuclei in Local 57 Ultra/luminous Infrared Galaxies Observed with NuSTAR and/or Swift/BAT
• Evolution of compact groups from intermediate to final stages: A case study of the HI content of HCG 16
• Deep Chandra Observations of HCG 16 - II. The Development of the Intra-group Medium in a Spiral-Rich Group
• Unsupervised Machine Learning for the Classification of Astrophysical X-ray Sources
• Cosmic Pathways for Compact Groups in the Milli-Millennium Simulation
• MeerKAT view of Hickson Compact Groups:I. Data description and release