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317 results on '"Gal, R. R."'

51. The VIMOS Ultra Deep Survey: The reversal of the star-formation rate − density relation at 2 < z < 5

Author

Lemaux, B. C., primary, Cucciati, O., additional, Le Fèvre, O., additional, Zamorani, G., additional, Lubin, L. M., additional, Hathi, N., additional, Ilbert, O., additional, Pelliccia, D., additional, Amorín, R., additional, Bardelli, S., additional, Cassata, P., additional, Gal, R. R., additional, Garilli, B., additional, Guaita, L., additional, Giavalisco, M., additional, Hung, D., additional, Koekemoer, A., additional, Maccagni, D., additional, Pentericci, L., additional, Ribeiro, B., additional, Schaerer, D., additional, Shah, E., additional, Shen, L., additional, Staab, P., additional, Talia, M., additional, Thomas, R., additional, Tomczak, A. R., additional, Tresse, L., additional, Vanzella, E., additional, Vergani, D., additional, and Zucca, E., additional

Published
2022
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53. An optical observational cluster mass function at z ∼ 1 with the ORELSE survey

Author

Hung, D., Lemaux, B. C., Gal, R. R., Tomczak, A. R., Lubin, L.M., Cucciati, O., Pelliccia, D., Shen, L., Le Fèvre, O., Zamorani, G., Wu, P.-F., Kocevski, D. D., Fassnacht, C.D., and Squires, G. K.

Subjects
Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

We present a new mass function of galaxy clusters and groups using optical/near-infrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. At z ∼ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ∼ 1 cluster mass functions are achievable without supplemental X-ray or Sunyaev-Zel’dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ∼240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M⊙) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ω_m, and the amplitude of fluctuations, σ₈, of Ω_m = 0.250−0.099+0.104 and σ₈ = 1.150−0.163+0.260⁠. While our Ω_m value is close to concordance, our σ₈ value is ∼2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.

Published
2021

60. The afterglow, redshift and extreme energetics of the gamma-ray burst of 23 January 1999

Author

Kulkarni, S. R., Djorgovski, S. G., Odewahn, S. C., Bloom, J. S., Gal, R. R., Koresko, C. D., Harrison, F. A., Lubin, L. M., Armus, L., Sari, R., Illingworth, G. D., Kelson, D. D., Magee, D. K., van Dokkum, P. G., Frail, D. A., Mulchaey, J. S., Malkan, M. A., McClean, I. S., Teplitz, H. I., Koerner, D., Kirkpatrick, D., Kobayashi, N., Yadigaroglu, I.-A., Halpern, J., Piran, T., Goodrich, R. W., Chaffee, F. H., Feroci, M., and Costa, E.

Published
1999

65. X-ray-emitting active galactic nuclei from z = 0.6 to 1.3 in the intermediate- and high-density environments of the ORELSE survey

Author

Rumbaugh, N., Lemaux, B. C., Tomczak, A., Kocevski, D. D., Lubin, L. M., Wu, P.-F., Gal, R. R., Shen, L., Mansheim, A., Fassnacht, C. D., and Squires, G. K.

Abstract

We studied active galactic nucleus (AGN) activity in 12 large-scale structures (LSSs) in the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey, at 0.65 < z < 1.28, using a combination of Chandra observations, optical and NIR imaging and spectroscopy. We located a total of 61 AGNs that were successfully matched to optical counterparts in the LSSs. We found that AGN populations across our sample had more recently had starburst events compared to the overall galaxy populations. We find no relation between AGN activity and location within the LSSs, suggesting triggering mechanisms that depend on global environment are at most sub-dominant. To focus on differences between our AGNs, we grouped them into four sub-samples based on the spectral properties of their parents LSSs. We found one of the sub-samples, SG0023 & SC1604, stood out from the others. AGNs in this sample were disproportionately luminous. These AGNs had the most recent starburst events, in contrast to their parent populations. Additionally, both the AGNs and the overall galaxy population in SG0023 & SC1604 had the largest fraction of close kinematic pairs, which indicates a higher rate of galaxy mergers and interactions. These results suggest that major mergers are driving AGN activity in SG0023 & SC1604, while other processes are likely triggering less luminous AGNs in the rest of our sample. Additionally, minor mergers are unlikely to play a significant role, since the same conditions that lead to more major mergers should also lead to more minor mergers, which is not observed in SG0023 & SC1604.

Published
2017

66. Establishing a new technique for discovering large-scale structure using the ORELSE survey.

Author

Hung, D, Lemaux, B C, Gal, R R, Tomczak, A R, Lubin, L M, Cucciati, O, Pelliccia, D, Shen, L, Le Fèvre, O, Wu, P-F, Kocevski, D D, Mei, S, and Squires, G K

Subjects
MONTE Carlo method, GALACTIC evolution, SPECTROSCOPIC imaging, GALAXY clusters, GALAXIES, CATALOGS, REDSHIFT
Abstract

The Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey is an ongoing imaging and spectroscopic campaign initially designed to study the effects of environment on galaxy evolution in high-redshift (z ∼ 1) large-scale structures. We use its rich data in combination with a powerful new technique, Voronoi tessellation Monte Carlo (VMC) mapping, to search for serendipitous galaxy overdensities at 0.55 < z < 1.37 within 15 ORELSE fields, a combined spectroscopic footprint of ∼1.4 deg2. Through extensive tests with both observational data and our own mock galaxy catalogues, we optimize the method's many free parameters to maximize its efficacy for general overdensity searches. Our overdensity search yielded 402 new overdensity candidates with precisely measured redshifts and an unprecedented sensitivity down to low total overdensity masses (⁠|$\mathcal {M}_{\mathrm{ tot}}\gtrsim5\times 10^{13}$| M⊙). Using the mock catalogues, we estimated the purity and completeness of our overdensity catalogue as a function of redshift, total mass, and spectroscopic redshift fraction, finding impressive levels of both 0.92/0.83 and 0.60/0.49 for purity/completeness at z  = 0.8 and z  = 1.2, respectively, for all overdensity masses at spectroscopic fractions of ∼20 per cent. With VMC mapping, we are able to measure precise systemic redshifts, provide an estimate of the total gravitating mass, and maintain high levels of purity and completeness at z ∼ 1 even with only moderate levels of spectroscopy. Other methods (e.g. red-sequence overdensities and hot medium reliant detections) begin to fail at similar redshifts, which attests to VMC mapping's potential to be a powerful tool for current and future wide-field galaxy evolution surveys at z ∼ 1 and beyond. [ABSTRACT FROM AUTHOR]

Published
2020
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68. Corrigendum: Hidden starbursts and active galactic nuclei at 0 < z < 4 from the Herschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback (Astronomy and Astrophysics (2014) 572 (A90) DOI: 10.1051/0004-6361/201323089)

Author

Lemaux, B. C., Le Floc’h, E., Le Fèvre, O., Ilbert, O., Tresse, L., Lubin, L. M., Zamorani, G., Gal, R. R., Ciliegi, P., Cassata, P., Kocevski, D. D., Mcgrath, E. J., Bardelli, S., Zucca, E., and Squires, G. K.

Subjects
Space and Planetary Science, Astronomy and Astrophysics
Published
2017

70. Suppressed star formation by a merging cluster system

Author

Mansheim, A. S., primary, Lemaux, B. C., additional, Tomczak, A. R., additional, Lubin, L. M., additional, Rumbaugh, N., additional, Wu, P.-F., additional, Gal, R. R., additional, Shen, L., additional, Dawson, W. A., additional, and Squires, G. K., additional

Published
2017
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71. Hidden starbursts and active galactic nuclei at 0 < z < 4 from the Herschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback (Corrigendum)

Author

Lemaux, B. C., primary, Le Floc’h, E., additional, Le Fèvre, O., additional, Ilbert, O., additional, Tresse, L., additional, Lubin, L. M., additional, Zamorani, G., additional, Gal, R. R., additional, Ciliegi, P., additional, Cassata, P., additional, Kocevski, D. D., additional, McGrath, E. J., additional, Bardelli, S., additional, Zucca, E., additional, and Squires, G. K., additional

Published
2016
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73. The Assembly of the Red Sequence at z ~ 1: The Color and Spectral Properties of Galaxies in the Cl1604 Supercluster

Author

Lemaux, B. C., Gal, R. R., Lubin, L. M., Kocevski, D. D., Fassnacht, C. D., McGrath, E. J., Squires, G. K., Surace, J. A., and Lacy, M.

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We investigate the properties of the 525 spectroscopically confirmed members of the Cl1604 supercluster at z ~ 0.9 as part of the Observations of Redshift Evolution in Large Scale Environments survey. In particular, we focus on the photometric, stellar mass, morphological, and spectral properties of the 305 member galaxies of the eight clusters and groups that comprise the Cl1604 supercluster. Using an extensive Keck Low-Resolution Imaging Spectrometer (LRIS)/DEep Imaging Multi-Object Spectrograph (DEIMOS) spectroscopic database in conjunction with ten-band ground-based, Spitzer, and Hubble Space Telescope imaging, we investigate the buildup of the red sequence in groups and clusters at high redshift. Nearly all of the brightest and most massive red-sequence galaxies present in the supercluster environment are found to lie within the bounds of the cluster and group systems, with a surprisingly large number of such galaxies present in low-mass group systems. Despite the prevalence of these red-sequence galaxies, we find that the average cluster galaxy has a spectrum indicative of a star-forming galaxy, with a star formation rate between those of z ~ 1 field galaxies and moderate-redshift cluster galaxies. The average group galaxy is even more active, exhibiting spectral properties indicative of a starburst. The presence of massive, red galaxies and the high fraction of starbursting galaxies present in the group environment suggest that significant processing is occurring in group environments at z ~ 1 and earlier. There is a deficit of low-luminosity red-sequence galaxies in all Cl1604 clusters and groups, suggesting that such galaxies transition to the red sequence at later times. Extremely massive (~10^(12)M_☉) red-sequence galaxies routinely observed in rich clusters at z ~ 0 are also absent from the Cl1604 clusters and groups. We suggest that such galaxies form at later times through merging processes. There are significant populations of transition galaxies at intermediate stellar masses (log(M_*)=10.25-10.75) present in the group and cluster environments, suggesting that this range is important for the buildup of the red-sequence mass function at z ~ 1. Through a comparison of the transitional populations present in the Cl1604 cluster and group systems, we find evidence that massive blue-cloud galaxies are quenched earliest in the most dynamically relaxed systems and at progressively later times in dynamically unrelaxed systems.

Published
2012

74. The Complex Structure of the Cl 1604 Supercluster at z ~ 0.9

Author

Gal, R. R., Lemaux, B. C., Lubin, L. M., Kocevski, D., and Squires, G. K.

Subjects
Caltech Library Services
Abstract

The Cl 1604 supercluster at z = 0.9 is one of a small handful of such structures discovered in the high-redshift universe and is the first target observed as part of the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. To date, Cl 1604 is the largest structure mapped at z ~ 1, with the most constituent clusters and the largest number of spectroscopically confirmed member galaxies. In this paper we present the results of a spectroscopic campaign to create a three-dimensional map of Cl 1604 and to understand the contamination by foreground and background large-scale structures. Combining new Deep Imaging Multi-Object Spectrograph observations with previous data yields high-quality redshifts for 1138 extragalactic objects in a ~0.08 deg^2 region, 413 of which are supercluster members. We examine the complex three-dimensional structure of Cl 1604, providing velocity dispersions for eight of the member clusters and groups. Our extensive spectroscopic data set is used to examine potential biases in cluster velocity dispersion measurements in the presence of overlapping structures and filaments. We also discuss other structures found along the line of sight, including a filament at z = 0.6 and two serendipitously discovered groups at z ~ 1.2.

Published
2008

75. Chronos and KAIROS: MOSFIRE observations of post-starburst galaxies in z ~ 1 clusters and groups.

Author

Lemaux, B. C., Tomczak, A. R., Lubin, L. M., Wu, P-F., Gal, R. R., Rumbaugh, N., Kocevski, D. D., and Squires, G. K.

Subjects
STARBURSTS, OPEN clusters of stars, REDSHIFT, GALACTIC evolution, DUST
Abstract

We present an exploration of ~500 spectroscopically confirmed galaxies in and around two large-scale structures (LSSs) at z ~ 1 drawn from the Observations of Redshift Evolution in Large Scale Environments survey, an ongoing, wide-field photometric and spectroscopic campaign targeting a large ensemble of LSSs at 0.6 < z < 1.3. A sub-sample of these galaxies (~150) was targeted for the initial phase of a near-infrared MOSFIRE spectroscopic campaign investigating the differences in selections of galaxies that had recently ended a burst of star formation and/or had rapidly quenched (i.e. post-starburst/K+A galaxies). Selection with MOSFIRE utilizing the Hα and [N II] emission features resulted in a post-starburst sample more than double that selected by traditional z ~ 1 (observed-frame optical) methods even after the removal of the relatively large fraction of dusty starburst galaxies selected through traditional methods. While the traditional post-starburst fraction increased with increasing global density, the MOSFIRE-selected post-starburst fraction was found to be constant across field, group, and cluster environments. However, this fraction computed relative to the number of star-forming galaxies was observed to elevate in the cluster environment. Post-starbursts selected with MOSFIRE exhibited moderately strong [O II] emission originating from activity other than star formation. Such galaxies, termed K+A with ImposteR [OII]-derived Star formation (KAIROS) galaxies, were found to be younger than and likely undergoing feedback absent or diminished in their optically selected counterparts. A comparison between the environments of the two types of post-starbursts suggested a picture in which the evolution of a post-starburst galaxy is considerably different in cluster environments than in the more rarefied environments of a group or the field. [ABSTRACT FROM AUTHOR]

Published
2017
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77. Exploration of Large Digital Sky Surveys

Author

Djorgovski, S. G., primary, Brunner, R. J., additional, Mahabal, A. A., additional, Odewahn, S. C., additional, Carvalho, R. R. de, additional, Gal, R. R., additional, Stolorz, P., additional, Granat, R., additional, Curkendall, D., additional, Jacob, J., additional, and Castro, S., additional

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78. Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

Author

Lemaux, B. C., primary, Le Floc’h, E., additional, Le Fèvre, O., additional, Ilbert, O., additional, Tresse, L., additional, Lubin, L. M., additional, Zamorani, G., additional, Gal, R. R., additional, Ciliegi, P., additional, Cassata, P., additional, Kocevski, D. D., additional, McGrath, E. J., additional, Bardelli, S., additional, Zucca, E., additional, and Squires, G. K., additional

Published
2014
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79. VIMOS Ultra-Deep Survey (VUDS): Witnessing the assembly of a massive cluster atz~ 3.3

Author

Lemaux, B. C., primary, Cucciati, O., additional, Tasca, L. A. M., additional, Le Fèvre, O., additional, Zamorani, G., additional, Cassata, P., additional, Garilli, B., additional, Le Brun, V., additional, Maccagni, D., additional, Pentericci, L., additional, Thomas, R., additional, Vanzella, E., additional, Zucca, E., additional, Amorín, R., additional, Bardelli, S., additional, Capak, P., additional, Cassarà, L. P., additional, Castellano, M., additional, Cimatti, A., additional, Cuby, J. G., additional, de la Torre, S., additional, Durkalec, A., additional, Fontana, A., additional, Giavalisco, M., additional, Grazian, A., additional, Hathi, N. P., additional, Ilbert, O., additional, Moreau, C., additional, Paltani, S., additional, Ribeiro, B., additional, Salvato, M., additional, Schaerer, D., additional, Scodeggio, M., additional, Sommariva, V., additional, Talia, M., additional, Taniguchi, Y., additional, Tresse, L., additional, Vergani, D., additional, Wang, P. W., additional, Charlot, S., additional, Contini, T., additional, Fotopoulou, S., additional, Gal, R. R., additional, Kocevski, D. D., additional, López-Sanjuan, C., additional, Lubin, L. M., additional, Mellier, Y., additional, Sadibekova, T., additional, and Scoville, N., additional

Published
2014
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81. The Voronoi Tessellation cluster finder in 2+1 dimensions

Author

Soares-Santos, M, de Carvalho, R R, Annis, J, Gal, R R, La Barbera, F, Lopes, P A A, Wechsler, R H, Busha, M T, Gerke, B F, Soares-Santos, M, de Carvalho, R R, Annis, J, Gal, R R, La Barbera, F, Lopes, P A A, Wechsler, R H, Busha, M T, and Gerke, B F

Abstract

We present a detailed description of the Voronoi Tessellation (VT) cluster finder algorithm in 2+1 dimensions, which improves on past implementations of this technique. The need for cluster finder algorithms able to produce reliable cluster catalogs up to redshift 1 or beyond and down to $10^{13.5}$ solar masses is paramount especially in light of upcoming surveys aiming at cosmological constraints from galaxy cluster number counts. We build the VT in photometric redshift shells and use the two-point correlation function of the galaxies in the field to both determine the density threshold for detection of cluster candidates and to establish their significance. This allows us to detect clusters in a self consistent way without any assumptions about their astrophysical properties. We apply the VT to mock catalogs which extend to redshift 1.4 reproducing the $\Lambda$CDM cosmology and the clustering properties observed in the SDSS data. An objective estimate of the cluster selection function in terms of the completeness and purity as a function of mass and redshift is as important as having a reliable cluster finder. We measure these quantities by matching the VT cluster catalog with the mock truth table. We show that the VT can produce a cluster catalog with completeness and purity $>80%$ for the redshift range up to $\sim 1$ and mass range down to $\sim 10^{13.5}$ solar masses.

Published
2010

86. Submillimetre source counts in the fields of high-redshift galaxy clusters

Author

Noble, A. G., primary, Webb, T. M. A., additional, Ellingson, E., additional, Faloon, A. J., additional, Gal, R. R., additional, Gladders, M. D., additional, Hicks, A. K., additional, Hoekstra, H., additional, Hsieh, B. C., additional, Ivison, R. J., additional, Lemaux, B. C., additional, Lubin, L. M., additional, O’Donnell, D. V., additional, and Yee, H. K. C., additional

Published
2011
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88. DECISION TREE CLASSIFIERS FOR STAR/GALAXY SEPARATION

Author

Vasconcellos, E. C., primary, de Carvalho, R. R., additional, Gal, R. R., additional, LaBarbera, F. L., additional, Capelato, H. V., additional, Frago Campos Velho, H., additional, Trevisan, M., additional, and Ruiz, R. S. R., additional

Published
2011
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96. Exploration of Large Digital Sky Surveys

Author

Banday, Anthony J., Zaroubi, Saleem, Bartelmann, Matthias, Djorgovski, S. G., Brunner, R. J., Mahabal, A. A., Odewahn, S. C., de Carvalho, R. R., Gal, R. R., Stolorz, P., Granat, R., Curkendall, D., Jacob, J., Castro, S., Banday, Anthony J., Zaroubi, Saleem, Bartelmann, Matthias, Djorgovski, S. G., Brunner, R. J., Mahabal, A. A., Odewahn, S. C., de Carvalho, R. R., Gal, R. R., Stolorz, P., Granat, R., Curkendall, D., Jacob, J., and Castro, S.

Abstract

We review some of the scientific opportunities and technical challenges posed by the exploration of the large digital sky surveys, in the context of a Virtual Observatory (VO). The VO paradigm will profoundly change the way observational astronomy is done. Clustering analysis techniques can be used to discover samples of rare, unusual, or even previously unknown types of astronomical objects and phenomena. Exploration of the previously poorly probed portions of the observable parameter space are especially promising. We illustrate some of the possible types of studies with examples drawn from DPOSS; much more complex and interesting applications are forthcoming. Development of the new tools needed for an efficient exploration of these vast data sets requires a synergy between astronomy and information sciences, with great potential returns for both fields.

Published
2001

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