Mark Brodwin

Bio: Mark Brodwin is an academic researcher. The author has contributed to research in topics: Star formation & Cluster (physics). The author has an hindex of 1, co-authored 1 publications receiving 14 citations.

The era of star formation in galaxy clusters: implications for the Euclid cluster survey

Abstract: We analyze the star formation properties of 16 infrared-selected, spectroscopically confirmed galaxy clusters at 1 1.35. Using infrared luminosities measured with deep Spitzer/Multiband Imaging Photometer for Spitzer observations at 24 μm, along with robust optical + IRAC photometric redshifts and spectral-energy-distribution-fitted stellar masses, we present the dust-obscured star-forming fractions, star formation rates, and specific star formation rates in these clusters as functions of redshift and projected clustercentric radius. We find that z ~ 1.4 represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster star formation at earlier times. Beyond this redshift, the fraction of star-forming cluster members increases monotonically toward the cluster centers. Indeed, the specific star formation rate in the cores of these distant clusters is consistent with field values at similar redshifts, indicating that at z > 1.4 environment-dependent quenching had not yet been established in ISCS clusters. By combining these observations with complementary studies showing a rapid increase in the active galactic nucleus (AGN) fraction, a stochastic star formation history, and a major merging episode at the same epoch in this cluster sample, we suggest that the starburst activity is likely merger-driven and that the subsequent quenching is due to feedback from merger-fueled AGNs. The totality of the evidence suggests we are witnessing the final quenching period that brings an end to the era of star formation in galaxy clusters and initiates the era of passive evolution.

The Evolution of Early-Type Galaxies in Distant Clusters

Abstract: We present results from an optical-IR photometric study of early-type galaxies in 19 galaxy clusters out to z=0.9. The galaxy sample is selected on the basis of morphologies determined from HST WFPC2 images, and is photometrically defined in the K-band to minimize redshift-dependent selection biases. The optical-IR colors of the early-type cluster galaxies become bluer with increasing redshift in a manner consistent with the passive evolution of an old stellar population formed at an early cosmic epoch. The degree of color evolution is similar for clusters at similar redshift, and does not depend strongly on the optical richness or X-ray luminosity of the cluster, suggesting that the history of early-type galaxies is relatively insensitive to environment. The slope of the color-magnitude relationship shows no significant change out to z=0.9, providing evidence that it arises from a correlation between galaxy mass and metallicity, not age. Finally, the intrinsic scatter in the optical-IR colors is small and nearly constant with redshift, indicating that the majority of giant, early-type galaxies in clusters share a common star formation history, with little perturbation due to uncorrelated episodes of later star formation. Taken together, our results are consistent with models in which most early-type galaxies in rich clusters are old, formed the majority of their stars at high redshift in a well-synchronized fashion, and evolved quiescently thereafter.

AGES: The AGN and Galaxy Evolution Survey

Abstract: The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7 deg{sup 2} of the Booetes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23,745 redshifts. There are well-defined galaxy samples in 10 bands (the B{sub W} , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 {mu}m, and MIPS 24 {mu}m bands) to a limiting magnitude of I < 20 mag for spectroscopy. For these galaxies, we obtained 18,163 redshifts from a sample of 35,200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085 < z < 0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24 {mu}m sources to fainter limiting magnitudes (I < 22.5 mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshiftmore » estimates are provided for all sources in the AGES samples.« less

The evolution of active galactic nuclei in clusters of galax ies to redshift 1.3

Abstract: We have measured the luminous AGN population in a large sample of clusters of galaxies and find evidence for a substantial increase in the cluster AGN population from z � 0.05 to z � 1.3. The present sample now includes 32 clusters of galaxies, including 15 clusters abo ve z = 0.4, which corresponds to a three-fold increase compared to our previous work at high redshift. At z < 0.4 we have obtained new observations of AGN candidates in six additional clusters and found no new luminous AGN in cluster members. Our total sample of 17 low-redshift clusters contains only two luminous AGN, while at high redshifts there are 18 such AGN, or an average of more than one per cluster. We have characterized the evolution of luminous X-ray AGN as the fraction of galaxies with MR < M ∗(z) + 1 that host AGN with rest-frame, hard X-ray [2‐10 keV] luminosities LX,H � 10 43 erg s -1 . The AGN fraction increases from fA = 0.134 +0.18 -0.087 % at a median z = 0.19 to fA = 1.00 +0.29 -0.23 % at a median z = 0.72. Our best estimate of the evolution is a factor of eight inc rease to z = 1 and the statistical significance of the increase is 3 .8�. This dramatic evolution is qualitatively similar to the ev olution of the starforming galaxy population in clusters known as the Butcher-Oemler effect. We discuss the implications of this result for the coevolution of black holes and galaxies in clu sters, the evolution of AGN feedback, searches for clusters with the Sunyaev-Zel’dovich effect, and the possi ble detection of environment-dependent downsizing. Subject headings: galaxies: active ‐ galaxies: clusters: general ‐ galaxies: evolution ‐ X-rays: galaxies ‐ X-rays: galaxies: clusters ‐ X-rays: general

The Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS): The Role of Environment and Self-Regulation in Galaxy Evolution at z ~ 1

Abstract: We evaluate the effects of environment and stellar mass on galaxy properties at 0.85 9.3 the well-known correlations between environment and properties such as star-forming fraction (f_SF), SFR, SSFR, D(4000), and color are already in place at z ~ 1. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment, and fixed stellar mass. The SSFR of star-forming galaxies at fixed environment is correlated with stellar mass; however, at fixed stellar mass it is independent of environment. The same trend exists for the D(4000) measures of both the star-forming and quiescent galaxies and shows that their properties are determined primarily by their stellar mass, not by their environment. Instead, it appears that environment's primary role is to control the fraction of star-forming galaxies. Using the spectra we identify candidate poststarburst galaxies and find that those with 9.3 1, or if the evolution of the self-quenching rate mirrors the evolution of the environmental-quenching rate at z > 1, regardless of which dominates.

The Ages of Passive Galaxies in a z=1.62 Protocluster

Abstract: We present a study of the relation between galaxy stellar age and mass for 14 members of the $z=162$ protocluster IRC 0218, using multiband imaging and HST G102 and G141 grism spectroscopy Using $UVJ$ colors to separate galaxies into star forming and quiescent populations, we find that at stellar masses $M_* \geq 10^{1085} M_{\odot}$, the quiescent fraction in the protocluster is $f_Q=10^{+000}_{-037}$, consistent with a $\sim 2\times $ enhancement relative to the field value, $f_Q=045^{+003}_{-003}$ At masses $10^{102} M_{\odot} \leq M_* \leq 10^{1085} M_{\odot}$, $f_Q$ in the cluster is $f_Q=040^{+020}_{-018}$, consistent with the field value of $f_Q=028^{+002}_{-002}$ Using galaxy $D_{n}(4000)$ values derived from the G102 spectroscopy, we find no relation between galaxy stellar age and mass These results may reflect the impact of merger-driven mass redistribution, which is plausible as this cluster is known to host many dry mergers Alternately, they may imply that the trend in $f_Q$ in IRC 0218 was imprinted over a short timescale in the protocluster's assembly history Comparing our results with those of other high-redshift studies and studies of clusters at $z\sim 1$, we determine that our observed relation between $f_Q$ and stellar mass only mildly evolves between $z\sim 16$ and $z \sim 1$, and only at stellar masses $M_* \leq 10^{1085} M_{\odot}$ Both the $z\sim 1$ and $z\sim 16$ results are in agreement that the red sequence in dense environments was already populated at high redshift, $z \ge 3$, placing constraints on the mechanism(s) responsible for quenching in dense environments at $z\ge 15$