The Nature of High Equivalent Width Lyman-α Galaxies

Details The Nature of High Equivalent Width Lyman-α Galaxies The Nature of High Equivalent Width Lyman-α Galaxies

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005aas...207.2209f&link_type=abstract

American Astronomical Society Meeting 207, #22.09; Bulletin of the American Astronomical Society, Vol. 37, p.1194

Astronomy and Astrophysics

Astronomy

Scientific paper

We present new results on the nature of the high equivalent width Lyα lines seen in high-redshift galaxies. These galaxies were identified on the basis of their large equivalent width Lyα emission, beyond the maximum expected for normal stellar populations. To be produced, this strong Lyα emission requires a strong ionizing continuum. Previous X-ray images and optical spectra show that this emission is not powered by active galactic nuclei. The optical colors of these galaxies provide a diagnostic of the stellar populations. The large equivalent widths seen in the Lyα line in these galaxies could be produced via star formation if the stellar photospheres are hotter than normal, which might be expected for star formation in low metallicity galaxies. They could also result from a top-heavy initial mass function. Both of these scenarios might be expected in primitive galaxies.
To investigate these galaxies, we have computed stellar population models using the stellar population synthesis code created by Bruzual and Charlot (2003). We will use these models to predict the equivalent width distribution of the Lyα line in these high-redshift galaxies. We will also be able to derive estimates of stellar masses and stellar population ages, and be able to determine if these systems are indeed young and relatively primitive. Furthermore, we are obtaining new deep broadband imaging data on high-redshift galaxies taken from the Large Area Lyman Alpha (LALA) survey. These observations will yield better equivalent width measurements and continuum colors than previous data has allowed. We will compare these colors with the expectations for hot stars. We will also be able to constrain the star-formation rate using the UV continuum light from these galaxies, which will provide a valuable comparison with star-formation rates derived from the Lyα luminosity alone.

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