Browsing by Subject "SIMILAR-TO 1"

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  • Balogh, Michael L.; Mcgee, Sean L.; Mok, Angus; Muzzin, Adam; van der Burg, Remco F. J.; Bower, Richard G.; Finoguenov, Alexis; Hoekstra, Henk; Lidman, Chris; Mulchaey, John S.; Noble, Allison; Parker, Laura C.; Tanaka, Masayuki; Wilman, David J.; Webb, Tracy; Wilson, Gillian; Yee, Howard K. C. (2016)
    We present an analysis of galaxies in groups and clusters at 0.8 <z <1.2, from the GCLASS and GEEC2 spectroscopic surveys. We compute a 'conversion fraction' f(convert) that represents the fraction of galaxies that were prematurely quenched by their environment. For massive galaxies, M-star > 10(10.3) M-circle dot, we find f(convert) similar to 0.4 in the groups and similar to 0.6 in the clusters, similar to comparable measurements at z = 0. This means the time between first accretion into a more massive halo and final star formation quenching is t(p) similar to 2 Gyr. This is substantially longer than the estimated time required for a galaxy's star formation rate to become zero once it starts to decline, suggesting there is a long delay time during which little differential evolution occurs. In contrast with local observations we find evidence that this delay time-scale may depend on stellarmass, with t(p) approaching t(Hubble) for M-star similar to 10(9.5) M-circle dot. The result suggests that the delay time must not only be much shorter than it is today, but may also depend on stellar mass in a way that is not consistent with a simple evolution in proportion to the dynamical time. Instead, we find the data are well-matched by a model in which the decline in star formation is due to 'overconsumption', the exhaustion of a gas reservoir through star formation and expulsion via modest outflows in the absence of cosmological accretion. Dynamical gas removal processes, which are likely dominant in quenching newly accreted satellites today, may play only a secondary role at z = 1.
  • Pawlik, M. M.; Wild, V.; Walcher, C. J.; Johansson, P. H.; Villforth, C.; Rowlands, K.; Mendez-Abreu, J.; Hewlett, T. (2016)
    We present a new morphological indicator designed for automated recognition of galaxies with faint asymmetric tidal features suggestive of an ongoing or past merger. We use the new indicator, together with pre-existing diagnostics of galaxy structure to study the role of galaxy mergers in inducing (post-) starburst spectral signatures in local galaxies, and investigate whether (post-) starburst galaxies play a role in the build-up of the 'red sequence'. Our morphological and structural analysis of an evolutionary sample of 335 (post-) starburst galaxies in the Sloan Digital Sky Survey DR7 with starburst ages 0 <t(SB) <0.6 Gyr, shows that 45 per cent of galaxies with young starbursts (t(SB) <0.1 Gyr) show signatures of an ongoing or past merger. This fraction declines with starburst age, and we find a good agreement between automated and visual classifications. The majority of the oldest (post-) starburst galaxies in our sample (t(SB) similar to 0.6 Gyr) have structural properties characteristic of early-type discs and are not as highly concentrated as the fully quenched galaxies commonly found on the 'red sequence' in the present day Universe. This suggests that, if (post-) starburst galaxies are a transition phase between active star-formation and quiescence, they do not attain the structure of presently quenched galaxies within the first 0.6 Gyr after the starburst.
  • Balogh, Michael L.; van der Burg, Remco F. J.; Muzzin, Adam; Rudnick, Gregory; Wilson, Gillian; Webb, Kristi; Biviano, Andrea; Boak, Kevin; Cerulo, Pierluigi; Chan, Jeffrey; Cooper, M. C.; Gilbank, David G.; Gwyn, Stephen; Lidman, Chris; Matharu, Jasleen; McGee, Sean L.; Old, Lyndsay; Pintos-Castro, Irene; Reeves, Andrew M. M.; Shipley, Heath; Vulcani, Benedetta; Yee, Howard K. C.; Alonso, M. Victoria; Bellhouse, Callum; Cooke, Kevin C.; Davidson, Anna; De Lucia, Gabriella; Demarco, Ricardo; Drakos, Nicole; Fillingham, Sean P.; Finoguenov, Alexis; Ben Forrest; Golledge, Caelan; Jablonka, Pascale; Garcia, Diego Lambas; McNab, Karen; Muriel, Hernan; Nantais, Julie B.; Noble, Allison; Parker, Laura C.; Petter, Grayson; Poggianti, Bianca M.; Townsend, Melinda; Valotto, Carlos; Webb, Tracy; Zaritsky, Dennis (2021)
    We present the first public data release of the GOGREEN (Gemini Observations of Galaxies in Rich Early Environments) and GCLASS (Gemini CLuster Astrophysics Spectroscopic Survey) surveys of galaxies in dense environments, spanning a redshift range 0.8 <z <1.5. The surveys consist of deep, multiwavelength photometry and extensive Gemini GMOS spectroscopy of galaxies in 26 overdense systems ranging in halo mass from small groups to the most massive clusters. The objective of both projects was primarily to understand how the evolution of galaxies is affected by their environment, and to determine the physical processes that lead to the quenching of star formation. There was an emphasis on obtaining unbiased spectroscopy over a wide stellar mass range (M greater than or similar to 2 x 10(10) M-circle dot), throughout and beyond the cluster virialized regions. The final spectroscopic sample includes 2771 unique objects, of which 2257 have reliable spectroscopic redshifts. Of these, 1704 have redshifts in the range 0.8 <z <1.5, and nearly 800 are confirmed cluster members. Imaging spans the full optical and near-infrared wavelength range, at depths comparable to the UltraVISTA survey, and includes Hubble Space Telescope/Wide Field Camera 3 F160W (GOGREEN) and F140W (GCLASS). This data release includes fully reduced images and spectra, with catalogues of advanced data products including redshifts, line strengths, star formation rates, stellar masses, and rest-frame colours. Here, we present an overview of the data, including an analysis of the spectroscopic completeness and redshift quality.
  • Biviano, A.; van der Burg, R. F. J.; Balogh, M. L.; Munari, E.; Cooper, M. C.; De Lucia, G.; Demarco, R.; Jablonka, P.; Muzzin, A.; Nantais, J.; Old, L. J.; Rudnick, G.; Vulcani, B.; Wilson, G.; Yee, H. K. C.; Zaritsky, D.; Cerulo, P.; Chan, J.; Finoguenov, A.; Gilbank, D.; Lidman, C.; Pintos-Castro, Irene; Shipley, H. (2021)
    Context. The study of galaxy cluster mass profiles (M(r)) provides constraints on the nature of dark matter and on physical processes affecting the mass distribution. The study of galaxy cluster velocity anisotropy profiles (beta (r)) informs the orbits of galaxies in clusters, which are related to their evolution. The combination of mass profiles and velocity anisotropy profiles allows us to determine the pseudo phase-space density profiles (Q(r)); numerical simulations predict that these profiles follow a simple power law in cluster-centric distance.Aims. We determine the mass, velocity anisotropy, and pseudo phase-space density profiles of clusters of galaxies at the highest redshifts investigated in detail to date.Methods. We exploited the combination of the GOGREEN and GCLASS spectroscopic data-sets for 14 clusters with mass M-200 >= 10(14) M-circle dot at redshifts 0.9 = 10(9.5) M-circle dot. We used the MAMPOSSt method to constrain several M(r) and beta (r) models, and we then inverted the Jeans equation to determine the ensemble cluster beta (r) in a non-parametric way. Finally, we combined the results of the M(r) and beta (r) analysis to determine Q(r) for the ensemble cluster.Results. The concentration c(200) of the ensemble cluster mass profile is in excellent agreement with predictions from Lambda cold dark matter (Lambda CDM) cosmological numerical simulations, and with previous determinations for clusters of similar mass and at similar redshifts, obtained from gravitational lensing and X-ray data. We see no significant difference between the total mass density and either the galaxy number density distributions or the stellar mass distribution. Star-forming galaxies are spatially significantly less concentrated than quiescent galaxies. The orbits of cluster galaxies are isotropic near the center and more radial outside. Star-forming galaxies and galaxies of low stellar mass tend to move on more radially elongated orbits than quiescent galaxies and galaxies of high stellar mass. The profile Q(r), determined using either the total mass or the number density profile, is very close to the power-law behavior predicted by numerical simulations.Conclusions. The internal dynamics of clusters at the highest redshift probed in detail to date are very similar to those of lower-redshift clusters, and in excellent agreement with predictions of numerical simulations. The clusters in our sample have already reached a high degree of dynamical relaxation.
  • McNab, Karen; Balogh, Michael L.; van der Burg, Remco F. J.; Forestell, Anya; Webb, Kristi; Vulcani, Benedetta; Rudnick, Gregory; Muzzin, Adam; Cooper, M. C.; McGee, Sean; Biviano, Andrea; Cerulo, Pierluigi; Chan, Jeffrey C. C.; De Lucia, Gabriella; Demarco, Ricardo; Finoguenov, Alexis; Forrest, Ben; Golledge, Caelan; Jablonka, Pascale; Lidman, Chris; Nantais, Julie; Old, Lyndsay; Pintos-Castro, Irene; Poggianti, Bianca; Reeves, Andrew M. M.; Wilson, Gillian; Yee, Howard K. C.; Zaritsky, Dennis (2021)
    We measure the rate of environmentally driven star formation quenching in galaxies at z similar to 1, using eleven massive () galaxy clusters spanning a redshift range 1.0 < z < 1.4 from the GOGREEN sample. We identify three different types of transition galaxies: 'green valley' (GV) galaxies identified from their rest-frame (NUV - V) and (V - J) colours; 'blue quiescent' (BQ) galaxies, found at the blue end of the quiescent sequence in (U - V) and (V - J) colour; and spectroscopic post-starburst (PSB) galaxies. We measure the abundance of these galaxies as a function of stellar mass and environment. For high-stellar mass galaxies (logM/M-circle dot > 10.5) we do not find any significant excess of transition galaxies in clusters, relative to a comparison field sample at the same redshift. It is likely that such galaxies were quenched prior to their accretion in the cluster, in group, filament, or protocluster environments. For lower stellar mass galaxies (9.5 < logM/M-circle dot < 10.5) there is a small but significant excess of transition galaxies in clusters, accounting for an additional similar to 5-10 percent of the population compared with the field. We show that our data are consistent with a scenario in which 20-30 percent of low-mass, star-forming galaxies in clusters are environmentally quenched every Gyr, and that this rate slowly declines from z = 1 to z = 0. While environmental quenching of these galaxies may include a long delay time during which star formation declines slowly, in most cases this must end with a rapid (tau < 1Gyr) decline in star formation rate.
  • Pawlik, M. M.; Aldeen, L. Taj; Wild, V.; Mendez-Abreu, J.; Lahen, N.; Johansson, P. H.; Jimenez, N.; Lucas, W.; Zheng, Y.; Walcher, C. J.; Rowlands, K. (2018)
    Post-starburst galaxies can be identified via the presence of prominent Hydrogen Balmer absorption lines in their spectra. We present a comprehensive study of the origin of strong Balmer lines in a volume-limited sample of 189 galaxies with 0.01 <z <0.05, log(M-star/M-circle dot) > 9.5 and projected axial ratio b/a > 0.32. We explore their structural properties, environments, emission lines, and star formation histories, and compare them to control samples of star-forming and quiescent galaxies, and simulated galaxy mergers. Excluding contaminants, in which the strong Balmer lines are most likely caused by dust-star geometry, we find evidence for three different pathways through the post-starburst phase, with most events occurring in intermediate-density environments: (1) a significant disruptive event, such as a gas-rich major merger, causing a starburst and growth of a spheroidal component, followed by quenching of the star formation (70 per cent of post-starburst galaxies at 9.5 <log(M-star/M-circle dot) <10.5 and 60 per cent at log(M-star/M-circle dot) > 10.5); (2) at 9.5 <log(M-star/M-circle dot) <10.5, stochastic star formation in blue-sequence galaxies, causing a weak burst and subsequent return to the blue sequence (30 per cent); (3) at log(M-star/M-circle dot) > 10.5, cyclic evolution of quiescent galaxies which gradually move towards the high-mass end of the red sequence through weak starbursts, possibly as a result of a merger with a smaller gas-rich companion (40 per cent). Our analysis suggests that active galactic nuclei (AGNs) are 'on' for 50 per cent of the duration of the post-starburst phase, meaning that traditional samples of post-starburst galaxies with strict emission-line cuts will be at least 50 per cent incomplete due to the exclusion of narrow-line AGNs.
  • Strazzullo, V.; Daddi, E.; Gobat, R.; Valentino, F.; Pannella, M.; Dickinson, M.; Renzini, A.; Brammer, G.; Onodera, M.; Finoguenov, A.; Cimatti, A.; Carollo, C. M.; Arimoto, N. (2016)
    We use. Hubble Space Telescope/WFC3 imaging to study the red population in the IR-selected, X-ray detected, low-mass cluster Cl J1449+0856 at z = 2, one of the few bona fide established clusters discovered at this redshift, and likely a typical progenitor of an average massive cluster today. This study explores the presence and significance of an early red sequence in the core of this structure, investigating the nature of red-sequence galaxies, highlighting environmental effects on cluster galaxy populations at high redshift, and at the same time underlining similarities and differences with other distant dense environments. Our results suggest that the red population in the core of Cl J1449+0856 is made of a mixture of quiescent and dusty star-forming galaxies, with a seedling of the future red sequence already growing in the very central cluster region, and already characterizing the inner cluster core with respect to lower-density environments. On the other hand, the color-magnitude diagram of this cluster is definitely different from that of lower-redshift z less than or similar to 1 clusters, as well as of some rare particularly evolved massive clusters at similar redshift, and it is suggestive of a transition phase between active star formation and passive evolution occurring in the protocluster and established lower-redshift cluster regimes.