Star Formation in High-Redshift Cluster Ellipticals

Abstract

We measure the star formation rates (SFRs) of massive ($M_{\star }>10^{10.1}{M}_{\odot }$) early-type galaxies (ETGs) in a sample of 11 high-redshift ($1.0<z<1.5$) galaxy clusters drawn from the IRAC Shallow Cluster Survey (ISCS). We identify ETGs visually from Hubble Space Telescope imaging and select likely cluster members as having either an appropriate spectroscopic redshift or red sequence color. Mid-infrared SFRs are measured using Spitzer 24 $\mu$m data for isolated cluster galaxies for which contamination by neighbors, and active galactic nuclei, can be ruled out. Cluster ETGs show enhanced specific star formation rates (sSFRs) compared to cluster galaxies in the local Universe, but have sSFRs more than four times lower than that of field ETGs at $1<z<1.5$. Relative to the late-type cluster population, isolated ETGs show substantially quenched mean SFRs, yet still contribute 12% of the overall star formation activity measured in $1<z<1.5$ clusters. We find that new ETGs are likely being formed in ISCS clusters; the fraction of cluster galaxies identified as ETGs increases from 34% to 56% from $z\sim 1.5\to 1.25$. While the fraction of cluster ETGs that are highly star-forming ($\text{SFR}\ge 26M_{\odot }$ yr${}^{-1}$) drops from 27% to 10% over the same period, their sSFRs are roughly constant. All these factors taken together suggest that, particularly at $z\gtrsim 1.25$, the events that created these distant cluster ETGs$-$likely mergers, at least among the most massive$-$were both recent and gas-rich.

12 pages, 8 figures. Accepted for publication in The Astrophysical Journal

References in corpus (24)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• EAZY: A Fast, Public Photometric Redshift Code
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• UltraVISTA: a new ultra-deep near-infrared survey in COSMOS
• PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function From z=0-1
• Kinematic Structure of Merger Remnants
• The 0.4 < z < 1.3 star formation history of the Universe as viewed in the far-infrared
• CIRS: Cluster Infall Regions in the Sloan Digital Sky Survey I. Infall Patterns and Mass Profiles
• The Spitzer Deep, Wide-Field Survey
• Evolution of the Color-Magnitude Relation in Galaxy Clusters at z ~1 from the ACS Intermediate Redshift Cluster Survey
• Dissipation and Extra Light in Galactic Nuclei: I. Gas-Rich Merger Remnants
• Photometric Redshifts in the IRAC Shallow Survey
• Clusters at Half Hubble Time: Galaxy Structure and Colors in RXJ0152.7-1357 and MS1054-03
• SPITZER IRS spectra of Virgo early type galaxies: detection of stellar silicate emission
• Evolution of the Color-Magnitude relation in High-Redshift Clusters: Early-type Galaxies in the Lynx Supercluster at z~1.26
• The Formation of Massive Cluster Galaxies
• Spitzer/MIPS 24um Observations of Galaxy Clusters: An Increasing Fraction of Obscured Star-forming Members from z=0.02 to z=0.83
• The Galaxy Cluster Mid-Infrared Luminosity Function at 1.3<z<3.2
• The Evolution of Dusty Star Formation and Stellar Mass Assembly in Clusters: Results from the IRAC 3.6um, 4.5um, 5.8um and 8.0um Cluster Luminosity Functions
• Mid infrared properties of distant infrared luminous galaxies
• Assembly of the Red Sequence in Infrared-Selected Galaxy Clusters from the IRAC Shallow Cluster Survey
• The mid-infrared colour-magnitude relation of early-type galaxies in the Coma cluster as measured by Spitzer-IRS
• Mass and Redshift Dependence of Star Formation in Relaxed Galaxy Clusters