Browsing by Subject "galaxies: evolution"

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  • Smolcic, V.; Miettinen, O.; Tomicic, N.; Zamorani, G.; Finoguenov, A.; Lemaux, B. C.; Aravena, M.; Capak, P.; Chiang, Y. -K.; Civano, F.; Delvecchio, I.; Ilbert, O.; Jurlin, N.; Karim, A.; Laigle, C.; Le Fevre, O.; Marchesi, S.; McCracken, H. J.; Riechers, D. A.; Salvato, M.; Schinnerer, E.; Tasca, L.; Toft, S. (2017)
    We investigate the environment of 23 submillimetre galaxies (SMGs) drawn from a signal-to-noise (S/N)-limited sample of SMGs originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey of a Cosmic Evolution Survey (COSMOS) subfield and then followed up with the Submillimetre Array and Plateau de Bure Interferometer at 890 mu m and 1.3 mm, respectively. These SMGs already have well-defined multiwavelength counterparts and redshifts. We also analyse the environments of four COSMOS SMGs spectroscopically confirmed to lie at redshifts z(spec) > 4 : 5, and one at z(spec) = 2 : 49 resulting in a total SMG sample size of 28. We search for overdensities using the COSMOS photometric redshifts based on over 30 UV-NIR photometric measurements including the new UltraVISTA data release 2 and Spitzer/SPLASH data, and reaching an accuracy of sigma(Delta z/(1+z)) = (1 + z) = 0 : 0067 (0 : 0155) at z <3 : 5 (> 3.5). To identify overdensities we apply the Voronoi tessellation analysis, and estimate the redshift-space overdensity estimator delta(g) as a function of distance from the SMG and/or overdensity centre. We test and validate our approach via simulations, X-ray detected groups or clusters, and spectroscopic verifications using VUDS and zCOSMOS catalogues which show that even with photometric redshifts in the COSMOS field we can e ffi ciently retrieve overdensities out to z approximate to 5. Our results yield that 11 out of 23 (48%) JCMT/AzTEC 1.1 mm SMGs occupy overdense environments. Considering the entire JCMT/AzTEC 1.1 mm S = N >= 4 sample and taking the expected fraction of spurious detections into account, this means that 35-61% of the SMGs in the S/N-limited sample occupy overdense environments. We perform an X-ray stacking analysis in the 0.5-2 keV band using a 32 '' aperture and our SMG positions, and find statistically significant detections. For our z <2 subsample we find an average flux of (4.0 +/- 0.8) x 10(-16) erg s(-1) cm(-2) and a corresponding total mass of M-200 = 2.8 x 10(13) M-circle dot. The z > 2 subsample yields an average flux of (1.3 +/- 0.5) x 10(-16) erg s(-1) cm(-2) and a corresponding total mass of M-200 = 2 x 10(13) M-circle dot. Our results suggest a higher occurrence of SMGs occupying overdense environments at z >= 3 than at z <3. This may be understood if highly star-forming galaxies can only be formed in the highest peaks of the density field tracing the most massive dark matter haloes at early cosmic epochs, while at later times cosmic structure may have matured su ffi ciently that more modest overdensities correspond to su ffi ciently massive haloes to form SMGs.
  • Jaffe, Yara L.; Verheijen, Marc A. W.; Haines, Chris P.; Yoon, Hyein; Cybulski, Ryan; Montero-Castano, Maria; Smith, Rory; Chung, Aeree; Deshev, Boris Z.; Fernandez, Ximena; van Gorkom, Jacqueline; Poggianti, Bianca M.; Yun, Min S.; Finoguenov, Alexis; Smith, Graham P.; Okabe, Nobuhiro (2016)
    In a hierarchical Universe clusters grow via the accretion of galaxies from the field, groups and even other clusters. As this happens, galaxies can lose and/or consume their gas reservoirs via different mechanisms, eventually quenching their star formation. We explore the diverse environmental histories of galaxies through a multiwavelength study of the combined effect of ram-pressure stripping and group 'processing' in Abell 963, a massive growing cluster at z = 0.2 from the Blind Ultra Deep HI Environmental Survey (BUDHIES). We incorporate hundreds of new optical redshifts (giving a total of 566 cluster members), as well as Subaru and XMM-Newton data from LoCuSS, to identify substructures and evaluate galaxy morphology, star formation activity, and HI content (via HI deficiencies and stacking) out to 3 x R-200. We find that Abell 963 is being fed by at least seven groups, that contribute to the large number of passive galaxies outside the cluster core. More massive groups have a higher fraction of passive and HI-poor galaxies, while low-mass groups host younger (often interacting) galaxies. For cluster galaxies not associated with groups we corroborate our previous finding that HI gas (if any) is significantly stripped via ram-pressure during their first passage through the intracluster medium, and find mild evidence for a starburst associated with this event. In addition, we find an overabundance of morphologically peculiar and/or star-forming galaxies near the cluster core. We speculate that these arise from the effect of groups passing through the cluster (post-processing). Our study highlights the importance of environmental quenching and the complexity added by evolving environments.
  • Gozaliasl, Ghassem; Finoguenov, Alexis; Tanaka, Masayuki; Dolag, Klaus; Montanari, Francesco; Kirkpatrick, Charles C.; Vardoulaki, Eleni; Khosroshahi, Habib G.; Salvato, Mara; Laigle, Clotilde; McCracken, Henry J.; Ilbert, Olivier; Cappelluti, Nico; Daddi, Emanuele; Hasinger, Guenther; Capak, Peter; Scoville, Nick Z.; Toft, Sune; Civano, Francesca; Griffiths, Richard E.; Balogh, Michael; Li, Yanxia; Ahoranta, Jussi; Mei, Simona; Iovino, Angela; Henriques, Bruno M. B.; Erfanianfar, Ghazaleh (2019)
    We present the results of a search for galaxy clusters and groups in the ∼2 deg2 of the COSMOS field using all available X-ray observations from the XMM-Newton and Chandra observatories.We reach an X-ray flux limit of 3 × 10−16 erg cm−2 s−1 in the 0.5-2 keV range, and identify 247 X-ray groups with M200c = 8 × 1012-3 × 1014M at a redshift range of 0.08 ≤ z < 1.53, using the multiband photometric redshift and the master spectroscopic redshift catalogues of the COSMOS. The X-ray centres of groups are determined using high-resolution Chandra imaging. We investigate the relations between the offset of the brightest group galaxies (BGGs) from halo X-ray centre and group properties and compare with predictions from semi-analytic models and hydrodynamical simulations. We find that BGG offset decreases with both increasing halo mass and decreasing redshift with no strong dependence on the X-ray flux and SNR. We show that the BGG offset decreases as a function of increasing magnitude gap with no considerable redshift-dependent trend. The stellar mass of BGGs in observations extends over a wider dynamic range compared to model predictions. At z < 0.5, the central dominant BGGs become more massive than those with large offsets by up to 0.3 dex, in agreement with model prediction. The observed and predicted log-normal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is ∼0.3 dex.
  • Richter, P.; Winkel, B.; Wakker, B. P.; Pingel, N. M.; Fox, A. J.; Heald, G.; Walterbos, R. A. M.; Fechner, C.; Ben Bekhti, N.; Gentile, G.; Zschaechner, L. (2018)
    We present a detailed analysis of the absorption properties of one of the tidal gas streams around the "Whale" galaxy NGC 4631 in the direction of the quasar 2MASS J12421031+3214268. Our study is based on ultraviolet spectral data obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST) and 21cm-data from the HALOGAS project and the Green Bank Telescope (GBT). We detect strong H I Ly alpha absorption in the velocity range +550 to +800 km s(-1) related to gas from a NGC 4631 tidal stream known as Spur 2. We measure a column density of log (N(H I/cm(-2))) = 18.68 +/- 0.15, indicating that the quasar sightline traces the outer boundary of Spur 2 as seen in the 21 cm data. Metal absorption in Spur 2 is detected in the lines of O I, C II, Si II, and Si III in a complex absorption pattern that reflects the multiphase nature of the gas. We find that the average neutral gas fraction in Spur 2 toward 2MASS J12421031+3214268 is only 14%. This implies that ionized gas dominates the total mass of Spur 2, which then may comprise more than 10(9)M(circle dot). No significant depletion of Si is observed, showing that Spur 2 does not contain significant amounts of dust. From the measured O I/H I column density ratio, we determine an alpha abundance in Spur 2 of 0.131(-0.05)(+0.07) solar ([alpha/H] = -0.90 +/- 0.16), which is substantially lower than what is observed in the NGC 4631 disk. The low metallicity and low dust content suggest that Spur 2 represents metal-deficient gas stripped off a gas-rich satellite galaxy during a recent encounter with NGC 4631.
  • Zheng, Yirui; Wild, Vivienne; Lahen, Natalia; Johansson, Peter H.; Law, David; Weaver, John R.; Jimenez, Noelia (2020)
    Recent integral field spectroscopic (IFS) surveys have revealed radial gradients in the optical spectral indices of post-starburst (PSB) galaxies, which can be used to constrain their formation histories. We study the spectral indices of post-processed mock IFS datacubes of binary merger simulations, carefully matched to the properties of the MaNGA IFS survey, with a variety of black hole (BH) feedback models, progenitor galaxies, orbits, and mass ratios. Based on our simulation sample, we find that only major mergers on prograde-prograde or retrograde-prograde orbits in combination with a mechanical BH feedback model can form galaxies with weak enough ongoing star formation, and therefore absent H alpha emission, to be selected by traditional PSB selection methods. We find strong fluctuations in nebular emission line strengths, even within the PSB phase, suggesting that H alpha selected PSBs are only a subsample of the underlying population. The global PSB population can be more robustly identified using stellar continuum-based approaches. The difficulty in reproducing the very young PSBs in simulations potentially indicates that new sub-resolution star formation recipes are required to properly model the process of star formation quenching. In our simulations, we find that the starburst peaks at the same time at all radii, but is stronger and more prolonged in the inner regions. This results in a strong time evolution in the radial gradients of the spectral indices that can be used to estimate the age of the starburst without reliance on detailed star formation histories from spectral synthesis models.
  • Strazzullo, V.; Coogan, R. T.; Daddi, E.; Sargent, M. T.; Gobat, R.; Valentino, F.; Bethermin, M.; Pannella, M.; Dickinson, M.; Renzini, A.; Arimoto, N.; Cimatti, A.; Dannerbauer, H.; Finoguenov, A.; Liu, D.; Onodera, M. (2018)
    We present Atacama Large Millimeter/submillimeter Array observations of the 870 mu m continuum and CO(4-3) line emission in the core of the galaxy cluster Cl J1449+0856 at z = 2, a near-IR-selected, X-ray-detected system in the mass range of typical progenitors of today's massive clusters. The 870 mu m map reveals six F-870 mu m > 0.5 mJy sources spread over an area of 0.07 arcmin(2), giving an overdensity of a factor of similar to 10 (6) with respect to blank-field counts down to F-870 mu m > 1 mJy (> 0.5 mJy). On the other hand, deep CO(4-3) follow-up confirms membership of three of these sources but suggests that the remaining three, including the brightest 870 mu m sources in the field (F-870 mu m greater than or similar to 2 mJy), are likely interlopers. The measurement of 870 mu m continuum and CO(4-3) line fluxes at the positions of previously known cluster members provides a deep probe of dusty star formation occurring in the core of this high-redshift structure, adding up to a total star formation rate of similar to 700 +/- 100 M-circle dot yr(-1) and yielding an integrated star formation rate density of similar to 10(4) M-circle dot yr(-1) Mpc(-3), five orders of magnitude larger than in the field at the same epoch, due to the concentration of star-forming galaxies in the small volume of the dense cluster core. The combination of these observations with previously available Hubble Space Telescope imaging highlights the presence in this same volume of a population of galaxies with already suppressed star formation. This diverse composition of galaxy populations in Cl J1449+0856 is especially highlighted at the very cluster center, where a complex assembly of quiescent and star-forming sources is likely forming the future brightest cluster galaxy.
  • Wang, Tao; Elbaz, David; Daddi, Emanuele; Finoguenov, Alexis; Liu, Daizhong; Schreiber, Corentin; Martin, Sergio; Strazzullo, Veronica; Valentino, Francesco; van der Burg, Remco; Zanella, Anita; Ciesla, Laure; Gobat, Raphael; Le Brun, Amandine; Pannella, Maurilio; Sargent, Mark; Shu, Xinwen; Tan, Qinghua; Cappelluti, Nico; Li, Yanxia (2016)
    We report the discovery of a remarkable concentration of massive galaxies with extended X-ray emission at z(spec) = 2.506, which contains 11 massive (M-* greater than or similar to 10(11) M-circle dot) galaxies in the central 80 kpc region (11.6 sigma overdensity). We have spectroscopically confirmed 17 member galaxies with 11 from CO and the remaining ones from Ha. The X-ray luminosity, stellar mass content, and velocity dispersion all point to a collapsed, cluster-sized dark matter halo with mass M-200c = 10(13.9 +/- 0.2) M-circle dot, making it the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive galaxies classified as quiescent. The star formation rate (SFR) in the 80 kpc core reaches similar to 3400 M-circle dot yr(-1) with a. gas depletion time of similar to 200 Myr, suggesting that we caught this cluster in rapid build-up of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst fraction (similar to 25%, compared to 3%-5% in the field). The presence of both a collapsed, cluster-sized halo and a predominant population of massive SFGs suggests that this structure could represent an important transition phase between protoclusters and mature clusters. It provides evidence that the main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster, providing new insights into massive cluster formation at early epochs. The large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation.
  • Crespo, N. Alvarez; Smolic, V.; Finoguenov, A.; Barrufet, L.; Aravena, M. (2021)
    Aims. Submillimetre galaxies (SMGs) are bright sources at submillimetre wavelengths (F-850 mu m>2-5 mJy). Made up of mostly of high-z galaxies (z>1), SMGs are amongst the most luminous dusty galaxies in the Universe. These galaxies are thought to be the progenitors of the massive elliptical galaxies in the local Universe and to reside in massive haloes at early epochs. Studying their environments and clustering strength is thus important to put these galaxies in a cosmological context.Methods. We present an environmental study of a sample of 116 SMGs in 96 ALMA observation fields, which were initially discovered with the AzTEC camera on ASTE and identified with high-resolution 1.25 mm ALMA imaging within the COSMOS survey field, having either spectroscopic or unambiguous photometric redshift. We analysed their environments making use of the latest release of the COSMOS photometric catalogue, COSMOS2015, a catalogue that contains precise photometric redshifts for more than half a million objects over the 2 deg(2) COSMOS field. We searched for dense galaxy environments computing the so-called overdensity parameter as a function of distance within a radius of 5 from the SMG. We validated this approach spectroscopically for those SMGs for which spectroscopic redshift is available. As an additional test, we searched for extended X-ray emission as a proxy for the hot intracluster medium, performing an X-ray stacking analysis in the 0.5-2 keV band with a 32 '' aperture and our SMG position using all available XMM-Newton and Chandra X-ray observations of the COSMOS field.Results. We find that 27% (31 out of 116) of the SMGs in our sample are located in a galactic dense environment; a fraction that is similar to previous studies. The spectroscopic redshift is known for 15 of these 31 sources, thus this photometric approach is tested using spectroscopy. We are able to confirm that 7 out of 15 SMGs lie in high-density peaks. However, the search for associated extended X-ray emission via an X-ray stacking analysis leads to a detection that is not statistically significant.
  • 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.
  • Davis, Timothy A.; van de Voort, Freeke; Rowlands, Kate; McAlpine, Stuart; Wild, Vivienne; Crain, Robert A. (2019)
    Post-starburst galaxies arc typically considered to be a transition population, en route to the red sequence after a recent quenching event. Despite this, recent observations have shown that these objects typically have large reservoirs of cold molecular gas. In this paper we study the star-forming gas properties of a large sample of post-starburst galaxies selected from the cosmological, hydrodynamical EAGLE simulations. These objects resemble observed high-mass post-starburst galaxies both spectroscopically and in terms of their space density, stellar mass distribution, and sizes. We find that the vast majority of simulated post-starburst galaxies have significant gas reservoirs, with star-forming gas masses approximate to 10(9) M-circle dot, in good agreement with those seen in observational samples. The simulation reproduces the observed time evolution of the gas fraction of the post-starburst galaxy population, with the average galaxy losing approximate to 90 per cent of its star-forming interstellar medium in only approximate to 600 Myr. A variety of gas consumption/loss processes are responsible for this rapid evolution, including mergers and environmental effects, while active galactic nuclei play only a secondary role. The fast evolution in the gas fraction of post-starburst galaxies is accompanied by a clear decrease in the efficiency of star formation due to a decrease in the dense gas fraction. We predict that forthcoming ALMA observations of the gas reservoirs of low-redshift post-starburst galaxies will show that the molecular gas is typically compact and has disturbed kinematics, reflecting the disruptive nature of many of the evolutionary pathways that build up the post-starburst galaxy population.
  • Furnell, Kate E.; Collins, Chris A.; Kelvin, Lee S.; Clerc, Nicolas; Baldry, Ivan K.; Finoguenov, Alexis; Erfanianfar, Ghazaleh; Comparat, Johan; Schneider, Donald P. (2018)
    We present a sample of 329 low-to intermediate-redshift (0.05 <z
  • Kalita, Boris S.; Daddi, Emanuele; Coogan, Rosemary T.; Delvecchio, Ivan; Gobat, Raphael; Valentino, Francesco; Strazzullo, Veronica; Tremou, Evangelia; Gomez-Guijarro, Carlos; Elbaz, David; Finoguenov, Alexis (2021)
    We report the detection of multiple faint radio sources, that we identify as active galactic nucleus (AGN) jets, within CLJ1449+0856 at z = 2 using 3 GHz Very Large Array observations. We study the effects of radio-jet-based kinetic feedback at high redshifts, which has been found to be crucial in low-redshift clusters to explain the observed thermodynamic properties of their intracluster medium (ICM). We investigate this interaction at an epoch featuring high levels of AGN activity and a transitional phase of ICM in regards to the likelihood of residual cold gas accretion. We measure a total flux of 30.6 +/- 3.3 mu Jy from the six detected jets. Their power contribution is estimated to be 1.2 (+/- 0.6) x 10(44) erg s(-1), although this value could be up to 4.7 x 10(44) erg s(-1). This is a factor of similar to 0.25-1.0 of the previously estimated instantaneous energy injection into the ICM of CLJ1449+0856 from AGN outflows and star formation that have already been found to be sufficient in globally offsetting the cooling flows in the cluster core. In line with the already detected abundance of star formation, this mode of feedback being distributed over multiple sites, contrary to a single central source observed at low redshifts, points to accretion of gas into the cluster centre. This also suggests a 'steady state' of the cluster featuring non-cool-core-like behaviour. Finally, we also examine the total infrared-radio luminosity ratio for the known sample of galaxies within the cluster core and find that dense environments do not have any serious consequence on the compliance of galaxies to the infrared-radio correlation.
  • Deshev, Boris; Finoguenov, Alexis; Verdugo, Miguel; Ziegler, Bodo; Park, Changbom; Hwang, Ho Seong; Haines, Christopher; Kamphuis, Peter; Tamm, Antti; Einasto, Maret; Hwang, Narae; Park, Byeong-Gon (2017)
    Aims. The mergers of galaxy clusters are the most energetic events in the Universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data, an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short-lived) burst of star formation? Methods. We obtained optical spectroscopy of > 400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to obtain a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of ten non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies into passive, star forming or recently quenched depending on their spectra. Results. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger (less than or similar to 0.4 Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at similar to 2 : 5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as approximately two thirds of all the recently quenched galaxies in our survey.
  • McAlpine, Stuart; Harrison, Chris M.; Rosario, David J.; Alexander, David M.; Ellison, Sara L.; Johansson, Peter H.; Patton, David R. (2020)
    We investigate the connection between galaxy-galaxy mergers and enhanced black hole (BH) growth using the cosmological hydrodynamical EAGLE simulation. We do this via three methods of analysis, investigating: the merger fraction of AGN, the AGN fraction of merging systems, and the AGN fraction of galaxies with close companions. In each case, we find an increased abundance of AGN within merging systems relative to control samples of inactive or isolated galaxies (by up to a factor of approximate to 3 depending on the analysis method used), confirming that mergers are enhancing BH accretion rates for at least a subset of the galaxy population. The greatest excess of AGN triggered via a merger are found in lower mass (M-* similar to 10(10) M-circle dot) gas rich (f(gas) > 0.2) central galaxies with lower mass BHs (M-BH similar to 10(7) M-circle dot) at lower redshifts (z <1). We find no enhancement of AGN triggered via mergers in more massive galaxies (M-* greater than or similar to 10(11) M-circle dot). The enhancement of AGN is not uniform throughout the phases of a merger, and instead peaks within the early remnants of merging systems (typically lagging approximate to 300 Myr post-coalescence of the two galaxies at z = 0.5). We argue that neither major (M-*,M-1/M-*,M-2 = 1/4) nor minor mergers (1/10 <M-*,M-1/M-*,M-2 <1/4) are statistically relevant for enhancing BH masses globally. Whilst at all redshifts the galaxies experiencing a merger have accretion rates that are on average 2-3 times that of isolated galaxies, the majority of mass that is accreted on to BHs occurs outside the periods of a merger. We compute that on average no more than 15 per cent of a BHs final day mass comes from the enhanced accretion rates triggered via a merger.
  • Balogh, Michael L.; Gilbank, David G.; Muzzin, Adam; Rudnick, Gregory; Cooper, Michael C.; Lidman, Chris; Biviano, Andrea; Demarco, Ricardo; McGee, Sean L.; Nantais, Julie B.; Noble, Allison; Old, Lyndsay; Wilson, Gillian; Yee, Howard K. C.; Bellhouse, Callum; Cerulo, Pierluigi; Chan, Jeffrey; Pintos-Castro, Irene; Simpson, Rane; van der Burg, Remco F. J.; Zaritsky, Dennis; Ziparo, Felicia; Victoria Alonso, Maria; Bower, Richard G.; De Lucia, Gabriella; Finoguenov, Alexis; Garcia Lambas, Diego; Muriel, Hernan; Parker, Laura C.; Rettura, Alessandro; Valotto, Carlos; Wetzel, Andrew (2017)
    We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 <z <1.5, selected to span a factor > 10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over lambda similar to 0.6-1.05 mu m, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes z' <24.25 and [3.6] mu m <22.5, and is therefore statistically complete for stellar masses M* greater than or similar to 10(10.3) M-circle dot, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning u through K, in addition to deep IRAC imaging at 3.6 mu m. The spectroscopy is similar to 50 per cent complete as of semester 17A, and we anticipate a final sample of similar to 500 new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT, and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius.
  • Ford, E. Darragh; Laigle, C.; Gozaliasl, G.; Pichon, C.; Devriendt, J.; Slyz, A.; Arnouts, S.; Dubois, Y.; Finoguenov, A.; Griffiths, R.; Kraljic, K.; Pan, H.; Peirani, S.; Sarron, F. (2019)
    Cosmic filaments are the channel through which galaxy groups assemble their mass. Cosmic connectivity, namely the number of filaments connected to a given group, is therefore expected to be an important ingredient in shaping group properties. The local connectivity is measured in COSMOS around X-ray-detected groups between redshift 0.5 and 1.2. To this end, large-scale filaments are extracted using the accurate photometric redshifts of the COSMOS2015 catalogue in two-dimensional slices of thickness 120 comoving Mpc centred on the group's redshift. The link between connectivity, group mass, and the properties of the brightest group galaxy (BGG) is investigated. The same measurement is carried out on mocks extracted from the light-cone of the hydrodynamical simulation HORIZON-AGN in order to control systematics. More massive groups are on average more connected. At fixed group mass in low-mass groups, BGG mass is slightly enhanced at high connectivity, while in high-mass groups BGG mass is lower at higher connectivity. Groups with a star-forming BGG have on average a lower connectivity at given mass. From the analysis of the HORIZON-AGN simulation, we postulate that different connectivities trace different paths of group mass assembly: at high group mass, groups with higher connectivity are more likely to have grown through a recent major merger, which might be in turn the reason for the quenching of the BGG. Future large-field photometric surveys, such as Euclid and LSST, will be able to confirm and extend these results by probing a wider mass range and a larger variety of environment.
  • Laigle, C.; Davidzon, I.; Ilbert, O.; Devriendt, J.; Kashino, D.; Pichon, C.; Capak, P.; Arnouts, S.; de la Torre, S.; Dubois, Y.; Gozaliasl, G.; Le Borgne, D.; Lilly, S.; McCracken, H. J.; Salvato, M.; Slyz, A. (2019)
    Using the light-cone from the cosmological hydrodynamical simulation horizon-AGN, we produced a photometric catalogue over 0 <z <4 with apparent magnitudes in COSMOS, Dark Energy Survey, Large Synoptic Survey Telescope (LSST)-like, and Euclid-like filters at depths comparable to these surveys. The virtual photometry accounts for the complex star formation history (SFH) and metal enrichment of horizon-AGN galaxies, and consistently includes magnitude errors, dust attenuation, and absorption by intergalactic medium. The COSMOS-like photometry is fitted in the same configuration as the COSMOS2015 catalogue. We then quantify random and systematic errors of photometric redshifts, stellar masses, and star formation rates (SFR). Photometric redshifts and redshift errors capture the same dependencies on magnitude and redshift as found in COSMOS2015, excluding the impact of source extraction. COSMOS-like stellar masses are well recovered with a dispersion typically lower than 0.1 dex. The simple SFHs and metallicities of the templates induce a systematic underestimation of stellar masses at z <1.5 by at most 0.12 dex. SFR estimates exhibit a dust-induced bimodality combined with a larger scatter (typically between 0.2 and 0.6 dex). We also use our mock catalogue to predict photometric redshifts and stellar masses in future imaging surveys. We stress that adding Euclid near-infrared photometry to the LSST-like baseline improves redshift accuracy especially at the faint end and decreases the outlier fraction by a factor similar to 2. It also considerably improves stellar masses, reducing the scatter up to a factor 3. It would therefore be mutually beneficial for LSST and Euclid to work in synergy.
  • Patton, David R.; Wilson, Kieran D.; Metrow, Colin J.; Ellison, Sara L.; Torrey, Paul; Brown, Westley; Hani, Maan H.; McAlpine, Stuart; Moreno, Jorge; Woo, Joanna (2020)
    We use the IllustrisTNG cosmological hydrodynamical simulations to investigate how the specific star formation rates (sSFRs) of massive galaxies (M-* > 10(10) M-circle dot) depend on the distance to their closest companions. We estimate sSFR enhancements by comparing with control samples that are matched in redshift, stellar mass, local density, and isolation, and we restrict our analysis to pairs with stellar mass ratios of 0.1 to 10. At small separations (similar to 15 kpc), the mean sSFR is enhanced by a factor of 2.0 +/- 0.1 in the flagship (110.7Mpc)(3) simulation (TNG100-1). Statistically significant enhancements extend out to 3D separations of 280 kpc in the (302.6Mpc)(3) simulation (TNG300-1). We find similar trends in the EAGLE and Illustris simulations, although their sSFR enhancements are lower than those in TNG100-1 by about a factor of two. Enhancements in IllustrisTNG galaxies are seen throughout the redshift range explored (0
  • Bianconi, M.; Smith, G. P.; Haines, C. P.; McGee, S. L.; Finoguenov, A.; Egami, E. (2020)
    We explore the connection between dust and star formation, in the context of environmental effects on galaxy evolution. In particular, we exploit the susceptibility of dust to external processes to assess the influence of dense environment on star-forming galaxies. We have selected cluster Abell 1758 from the Local Cluster Substructure Survey (LoCuSS). Its complex dynamical state is an ideal test-bench to track dust removal and destruction in galaxies due to merger and accretion shocks. We present a systematic panchromatic study (from 0.15 mu m with GALEX to 500 mu m with Herschel) of spectroscopically confirmed star-forming cluster galaxies at intermediate redshift. We observe that the main subclusters (A1758N and A1758S) belong to two separate large-scale structures, with no overlapping galaxy members. Star forming cluster members are found preferentially outside cluster central regions, and are not isotropically distributed. Rather, these galaxies appear being funneled towards the main subclusters along separate accretion paths. Additionally, we present the first study of dust-to-stellar (DTS) mass ratio used as an indicator for local environmental influence on galaxy evolution. Star-forming cluster members show lower mean values (32 per cent at 2.4 sigma) of DTS mass ratio and lower levels of infrared emission from birth clouds with respect to coeval star-forming field galaxies. This picture is consistent with the majority of star-forming cluster members infalling in isolation. Upon accretion, star formation is observed to decrease and warm dust is destroyed due to heating from the intracluster medium radiation, ram-pressure stripping, and merger shocks.
  • Bianconi, M.; Smith, G. P.; Haines, C. P.; McGee, S. L.; Finoguenov, A.; Egami, E. (2018)
    We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via theirX-ray emission in the infall regions of 23 massive (<M-200 > = 10(15) M-circle dot) clusters at 0.15 <z <0.3. Highly complete spectroscopic coverage combined with 24 mu m imaging from Spitzer allows us to make a consistent and robust selection of cluster and group members including star-forming galaxies down to a stellar mass limit of M* = 2 x 10(10) M-circle dot. The fraction f(SF) of star-forming galaxies in infalling groups is lower and with a flatter trend with respect to clustercentric radius when compared to the rest of the cluster galaxy population. At R approximate to 1.3 r(200), the fraction of star-forming galaxies in infalling groups is half that in the cluster galaxy population. This is direct evidence that star-formation quenching is effective in galaxies already prior to them settling in the cluster potential, and that groups are favourable locations for this process.