The impact of starbursts and post-starbursts on the photometric evolution of high redshift galaxies

Abstract

We present evolutionary synthesis models for galaxies of spectral types Sa through Sd with starbursts of various strengths triggered at various redshifts and study their photometric evolution before, during, and after their bursts in a cosmological context. We find that bursts at high redshift, even very strong ones, only cause a small blueing of their intrinsically blue young parent galaxies. At lower redshift, in contrast, even small bursts cause a significant blueing of their intrinsically redder galaxies. While the burst phase is generally short, typically a few hundred Myr in normal-mass galaxies, the postburst stage with its red colors and, in particular the very red ones for early bursts at high redshift, lasts much longer, on the order of several Gyr. We find that, even without any dust, which in the postburst stage is not expected to play an important role anyway, models easily reach the colors of EROs in the redshift range z ∼ 2 through z ∼ 0.5 after starbursts at redshifts between 2 and 4. We therefore propose a third alternative for the ERO galaxies beyond the two established ones of passive galaxies vs. dusty starbursts: the dust-free post-(strong-)starbursts. A very first comparison of our models to HDF data with photometric redshifts shows that almost all of the outliers that could not be described with our chemically consistent models for undisturbed normal galaxy types E through Sd can now be explained very well. Galaxies in the redshift range from z ∼ 2.5 to z ∼ 0.5 that are redder, and in some cases much redder, than our reddest undisturbed model for a high-metallicity classical elliptical are well described by post-starburst models after starbursts at redshifts between 2 and 4. Galaxies bluer than our bluest low metallicity Sd model, most of which have redshifts lower than 1, are well explained by ongoing starbursts.

Systematic differences in simple stellar population model results: application to the M31 globular-like cluster system

“…Alvensleben & Fricke ; Fritze‐v. Alvensleben & Bicker ; Kotulla et al ). The recently updated BS‐SSP models (Xin et al ) considered the effects of blue straggler stars (BSs), which are likely the products of binary mergers and which seem to have a common occurrence in star clusters (see e.g.…”

“…Consequently, stellar population synthesis has become an important and powerful tool to interpret the nature of extragalactic star clusters, including their ages, metallicities, reddening values and masses. In the past few decades, many different simple stellar population (SSP) synthesis models have been constructed and applied to study extragalactic star clusters based on photometry in multiple passbands, including Bruzual & Charlot (1993); Worthey (1994); Leitherer & Heckman (1995); Fioc & Rocca-Volmerange ⋆ E-mail: zfan@bao.ac.cn † E-mail: grijs@pku.edu.cn (1997); Maraston (1998); Vazdekis (1999); Bruzual & Charlot (2003); Yi et al (2003); Maraston (2005); Conroy et al (2009); Xin et al (2011), as well as the GALEV models (see, e.g., Schulz et al 2002Schulz et al , 2003Fritze-v. Alvensleben & Bicker 2006;Kotulla et al 2009). The recently updated BS-SSP models (Xin et al 2011) considered the effects of blue straggler stars (BSs), which are likely the products of binary mergers and which seem a common occurrence in star clusters (see, e.g., Ahumada & Lapasset 1995;Piotto et al 2002;Xin et al 2011).…”

PopStar I: evolutionary synthesis model description

“…There have been in the past many studies devoted to the computation of integrated properties of SSPs, for example Bressan, Chiosi & Fagotto (1994), Bruzual & Charlot (2003, hereafter BC03), Leitherer et al (1999, hereafter STB99), Bicker et al (2004), González Delgado et al (2005, hereafter GON05), Maraston (2005, hereafter MAR05) and Fritze‐v. Alvensleben & Bicker (2006).…”

Astrophysics in 2006

“…You want a red spiral? OK, but you will have to go back to z = 1-2, where Roche et al (2006) found some, along with spheroidals and mergers, among EROs (extremely red objects), an observation duly confirmed by theory (Fritze-v.Alvensleben and Bicker 2006).…”