Spectroscopic study of blue compact galaxies

Abstract

Abstract. This is the fourth paper in a series studying star formation rates, stellar components, metallicities, and star formation histories of a blue compact galaxy (BCG) sample. Using Hα, [O ]λ3727, infrared (IR), radio (1.4 GHz) luminosities and neutral hydrogen (H ) gas masses, we estimated star formation rates and gas depletion timescales of 72 star-forming BCGs. The star formation rates of the BCGs in our sample span nearly four orders of magnitude, from approximately 10 −2 to 10 2 M yr −1 , with a median star formation rate of about 3 M yr −1 . The typical gas depletion timescale of BCGs is about one billion years. Star formation could be sustained at the current level only on a timescale significantly lower than the age of the universe before their neutral gas reservoir is completely depleted. To assess the possible systematic differences among different star formation rate indicators, we compared the star formation rates derived from Hα, [O ]λ3727, IR, and radio luminosities, and investigated the effects from underlying stellar absorption and dust extinction. We found that subtracting underlying stellar absorption is very important to calculate both dust extinction and star formation rate of galaxies. Otherwise, the intrinsic extinction will be overestimated, the star formation rates derived from [O ]λ3727 and Hα will be underestimated (if the underlying stellar absorption and the internal extinction were not corrected from the observed luminosity) or overestimated (if an overestimated internal extinction were used for extinction correction). After both the underlying stellar absorption and the dust extinction were corrected, a remarkably good correlation emerges among Hα, [O ]λ3727, IR and radio star formation rate indicators. Finally, we find a good correlation between the measured star formation rate and the absolute blue magnitude, metallicity, interstellar extinction of BCGs. Our results indicate that faint, low-mass BCGs have lower star formation rates.

Mapping the properties of blue compact dwarf galaxies: integral field spectroscopy with PMAS

“…I Zw 123 is a relatively wellstudied object: optical surface photometry was published in several papers (Cairós et al 2001a,b;Gil de Paz et al 2003;Caon et al 2005;Amorín et al 2007), and NIR photometry in Cairós et al (2003). A thorough spectroscopic study, including an analysis of its stellar content in terms of population synthesis models, was published in the series of papers by , , Kong et al (2003), Kong (2004) and Shi et al (2005).…”

“…Doublier et al (1997), Doublier et al (1999), Gil de Paz et al (2003 and Gil de Paz & Madore (2005). It is also included in the spectroscopy study of BCDs by , , Kong et al (2003), Kong (2004) and Shi et al (2005), and is the only object in our sample in common with the sample of galaxies studied by means of IFS by Petrosian et al (2002).…”

Astrophysics in 2005

“…The factual statement remains true, for example 10 7 -10 8.3 yr for luminous compact blue galaxies (Garland et al 2005), at most 10 9 yr for blue compact dwarfs (Kong 2004), right on out to a lensed galaxy (Sheth et al 2004). Gas exhaustion has been z p 2.5 ubiquitous since about .…”

The Xinglong 2.16-m Telescope: Current Instruments and Scientific Projects

“…An Hα imaging survey of ∼1400 nearby ALFALFA galaxies is carried out to study the star formation rate and the stellar distributions. From 1997 to 2002, the spectra of ∼ 100 blue compact galaxies (BCGs), which was the largest sample before SDSS, have been observed with the 2.16-m telescope, and the metallicity, extinction of dust, star formation rate of the sample galaxies have been derived by Kong & Cheng (2002a); Kong et al (2002b); Kong (2004); Shi et al (2005); Kong et al (2002b). A group of Peking University has discovered a high redshift quasar (z = 5.06), J2202+1509, in November 2014 with the 2.16-m telescope, which is SDSS i = 18.79 mag (the paper is in preparation).…”