The ACS NEARBY GALAXY SURVEY TREASURY. VII. the NGC4214 starburst and the effects of star formation history on dwarf morphology

Benjamin F. Williams, Julianne J. Dalcanton, Karoline M. Gilbert, Anil C. Seth, Daniel R. Weisz, Evan D. Skillman, Andrew E. Dolphin

Research output: Contribution to journalReview articlepeer-review

12 Scopus citations

Abstract

We present deep Hubble Space Telescope WFPC2 optical observations obtained as part of the ACS Nearby Galaxy Survey Treasury as well as early release Wide Field Camera 3 ultraviolet and infrared observations of the nearby dwarf starbursting galaxy NGC4214. Our data provide a detailed example of how covering such a broad range in wavelength provides a powerful tool for constraining the physical properties of stellar populations. The deepest data reach the ancient red clump at M F814W - 0.2. All of the optical data reach the main-sequence turnoff for stars younger than 300Myr and the blue He-burning sequence for stars younger than 500Myr. The full color-magnitude diagram (CMD) fitting analysis shows that all three fields in our data set are consistent with 75% of the stellar mass being older than 8 Gyr, in spite of showing a wide range in star formation rates at present. Thus, our results suggest that the scale length of NGC4214 has remained relatively constant for many gigayears. As previously noted by others, we also find the galaxy has recently ramped up production consistent with its bright UV luminosity and its population of UV-bright massive stars. In the central field we find UV point sources with F336W magnitudes as bright as -9.9. These are as bright as stars with masses of at least 52-56 M and ages near 4Myr in stellar evolution models. Assuming a standard initial mass function, our CMD is well fitted by an increase in star formation rate beginning 100Myr ago. The stellar populations of this late-type dwarf are compared with those of NGC404, an early-type dwarf that is also the most massive galaxy in its local environment. The late-type dwarf appears to have a similar high fraction of ancient stars, suggesting that these dominant galaxies may form at early epochs even if they have low total mass and very different present-day morphologies.

Original languageEnglish (US)
Article number22
JournalAstrophysical Journal
Volume735
Issue number1
DOIs
StatePublished - Jul 1 2011

Keywords

  • galaxies: evolution
  • galaxies: individual (NGC-4214)
  • galaxies: spiral
  • galaxies: stellar content

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