Hubble Space Telescope Grism Spectroscopy Of Extreme Starbursts Across Cosmic Time: The Role Of Dwarf Galaxies In The Star Formation History Of The Universe

Hakim Atek, Jean-Paul Richard Kneib
American Astronomical Society, 2014
Article

Résumé

Near infrared slitless spectroscopy with the Wide Field Camera 3, on board the Hubble Space Telescope, offers a unique opportunity to study low-mass galaxy populations at high redshift (z similar to 1-2). While most high-z surveys are biased toward massive galaxies, we are able to select sources via their emission lines that have very faint continua. We investigate the star formation rate (SFR)-stellar mass (M-star) relation for about 1000 emission line galaxies identified over a wide redshift range of 0.3 less than or similar to z less than or similar to 2.3. We use the Ha emission as an accurate SFR indicator and correct the broadband photometry for the strong nebular contribution to derive accurate stellar masses down to M-star similar to 10(7) M-circle dot. We focus here on a subsample of galaxies that show extremely strong emission lines (EELGs) with rest-frame equivalent widths ranging from 200 to 1500 A. This population consists of outliers to the normal SFR-M-star sequence with much higher specific SFRs (> 10 Gyr(-1)). While on-sequence galaxies follow continuous star formation processes, EELGs are thought to be caught during an extreme burst of star formation that can double their stellar mass in a period of less than 100 Myr. The contribution of the starburst population to the total star formation density appears to be larger than what has been reported for more massive galaxies in previous studies. In the complete mass range 8.2 < log(M-star/M-circle dot)< 10 and a SFR lower completeness limit of about 2 M-circle dot yr(-1) (10 M-circle dot yr-1) at z similar to 1 (z similar to 2), we find that starbursts having EWrest(H alpha) > 300, 200, and 100 angstrom contribute up to similar to 13%, 18%, and 34%, respectively, to the total SFR of emission-line-selected sample at z similar to 1-2. The comparison with samples of massive galaxies shows an increase in the contribution of starbursts toward lower masses.

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Hakim Atek, Jean-Paul Richard Kneib
American Astronomical Society, 2014
Article

Résumé

Official source

https://infoscience.epfl.ch/record/201217?ln=fr

À propos de ce résultat

Concepts associés (19)

Concepts associés

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Publications associées (69)

Publications associées

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The STAGES view of red spirals and dusty red galaxies: mass-dependent quenching of star formation in cluster infall

We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift similar to 0.17 using rest-frame near-ultraviolet-optical spectral energy distributions, 24-mu m infrared data and Hubble Space Telescope morphologies from the STAGES data set. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigma(cz) approximate to 2000 km s(-1). We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only four times lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M-/M-circle dot = [10, 11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific star formation rate (SFR) of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M-/M-circle dot < 10, such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note that edge-on spirals play a minor role; despite being dust reddened they form only a small fraction of spirals independent of environment.

Blackwell Publishing Ltd, Oxford2009

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LESS THAN 10 PERCENT OF STAR FORMATION IN z similar to 0.6 MASSIVE GALAXIES IS TRIGGERED BY MAJOR INTERACTIONS

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We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z similar to 0.4-0.9) and present the lens redshift for six of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile (Delta Sigma proportional to R-0.86 +/- 0.16) that is within 1 sigma of an isothermal profile (Delta Sigma proportional to R-1) with velocity dispersion sigma(upsilon) = 260 +/- 20 km s(-1). Additionally, we use a two-component de Vaucouleurs + Navarro-Frenk-White (NFW) model to disentangle the total mass profile into separate luminous and dark matter components and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (gamma(V) = 4.0 +/- 0.6hM(circle dot)/L-circle dot) and virial mass-to-light ratio (tau(V) = 300 +/- 90h M-circle dot/L-circle dot) for our sample, resulting in a virial-to-stellar mass ratio of M-vir/M-* = 75 +/- 25. Relaxing the NFW assumption, we estimate that changing the inner slope of the dark matter profile by similar to 20% yields a similar to 30% change in stellar mass-to-light ratio. Finally, we compare our results to a previous study using low-redshift lenses to understand how galaxy mass profiles evolve over time. We investigate the evolution of M-vir/M-(z) = alpha(1 + z)(beta), and find best-fit parameters of alpha = 51 +/- 36 and beta = 0.9 +/- 1.8, constraining the growth of virial-to-stellar mass ratio over the last similar to 7 Gyr. We note that, by using a sample of strong lenses, we are able to constrain the growth of M-vir/M-(z) without making any assumptions about the initial mass function of the stellar population.

2010

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