2009/12/29 by James A. Rose, Paul Robertson, Jesse Miner +1 · 16 citations
Chemistry · Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Physics #Spiral galaxy #Star formation #Stellar mass #astro-ph.CO
paper · pdf · doi:10.1088/0004-6256/139/2/765
published in The Astronomical Journal 139(2), 765-782 (Institute of Physics) · Accepted for publication by the Astronomical Journal
arxiv created 2009/12/29 · openalex publication_date 2010/01/14 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Broadband B and R and Hα images have been obtained with the 4.1 m SOAR telescope atop Cerro Pachon, Chile, for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low-density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (H i ) data obtained with the Arecibo 305 m radio telescope, acquired by Levy et al. (2007) and by Springob et al. (2005b), we study the star formation rates in disk galaxies as a function of their H i deficiency. To quantify H i deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of Hα flux to R-band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more H i -deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more H i -deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the H i -depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas depletion and the size of the Hα disk (relative to the R-band disk); H i -poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the Hα disks of gas-poor galaxies than in gas-rich spirals. Thus, both disk truncation and lowered SSFR levels within the star-forming part of the disks (aside from the enhanced nuclear SSFR) correlate with H i deficiency, and both phenomena are found to contribute equally to the global suppression of star formation. We compare our results found in the low-richness Pegasus I cluster and in non-cluster environments with SFRs found for H i -deficient spirals in the Virgo cluster by Koopmann & Kenney and Fumagalli & Gavazzi.