Panchromatic Study of Nearby Ultraviolet-bright Starburst Galaxies: Implications for Massive Star Formation and High-Redshift Galaxies

Abstract

We present a panchromatic study of nearby starburst galaxies from the ultraviolet to the visible, including narrow band Hα using WIYN and HST data, to determine how star formation processes affect the morphology and integrated fluxes of nearby starbursts. We find the UV/Hα morphology of starbursts tend to differ, although not in a standard or predictable manner. From our sample of six nearby starbursts, three systems show a good correlation between UV and Hα fluxes, but we find differences in UV and Hα morphology between the other three. Occasionally we find systems with well defined H II regions without the corresponding brightness in the UV, and vice-versa. We discuss the likely mechanisms behind these differences which include: starburst ages, dust absorption, stellar energy ejecta through SNe and winds, as well as leakage of UV photons from stellar clusters. We conclude that the large scale morphological features in starbursts are primarily due to both age and absorption from a 'picket fence' dust distribution.We further demonstrate the similarity and differences between these nearby starbursts and high redshift star forming galaxies. The overall morphology of our sample of starbursts changes little between UV and visible wavelengths. If high redshift galaxies are similar to these starbursts, their morphologies should change little between rest-frame UV and optical. We also show that FIR and UV spectral energy distributions and slopes can be used to determine large scale morphological features for extreme starbursts, with the steepest FIR slopes correlating with the most disturbed galaxies.

Thermal and non-thermal components of the interstellar medium at sub-kiloparsec scales in galaxies

“…This is a typical ringed galaxy. Conselice et al (2000) suggest that the nuclear starburst in this galaxy is due to the dynamical influence of the prominent bar. In the BIMA image the gas appears concentrated nearly entirely along the "twin peaked" area of the nuclear region (Kenney et al 1992).…”

The star cluster system of the NGC 7673 starburst

“…7, we would not expect all of the clusters to escape the effects of dust extinction. However, we might expect to see only weak dust effects in our sample, because we are heavily biased in favor of clusters which do not have significant reddening (for a discussion see Conselice et al 2000b andCalzetti 2001). One magnitude of visual extinction makes a cluster approximately 2.4 mag fainter in our F255W filter.…”

The H$\mathsf{\alpha}$ galaxy survey

“…The sample contains a large number of Magellanic irregular galaxies, and these show an interesting variety in star formation morphologies. UGC 7326 (classified Im), UGC 7866 (an IABm) and UGC 8098 (an SBm, also named NGC 4861; see also Conselice et al 2000 who present ground-based and Hubble Space Telescope imaging of this galaxy) all show highly asymmetric or "cometary" morphologies ( Fig. 9) in their continuum-subtracted Hα+[N] images, with extremely intense star formation centres which are displaced very significantly from the centres of the old stellar distributions.…”