Browsing by Subject "galaxies: high-redshift"

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  • Valentino, Francesco; Daddi, Emanuele; Finoguenov, Alexis; Strazzullo, Veronica; Le Brun, Amandine; Vignali, Cristian; Bournaud, Frederic; Dickinson, Mark; Renzini, Alvio; Bethermin, Matthieu; Zanella, Anita; Gobat, Raphael; Cimatti, Andrea; Elbaz, David; Onodera, Masato; Pannella, Maurilio; Sargent, Mark; Arimoto, Nobuo; Carollo, Marcella; Starck, Jean-Luc (2016)
    We present the discovery of a giant >= 100 kpc Ly alpha nebula detected in the core of the X-ray emitting cluster CL J1449 +0856 at z = 1.99 through Keck/LRIS narrow-band imaging. This detection extends the known relation between Lya nebulae and overdense regions of the universe to the dense core of a 5-7 x 10(13) M-circle dot cluster. The most plausible candidates to power the nebula are two Chandra-detected AGN host cluster members, while cooling from the X-ray phase and cosmological cold flows are disfavored primarily because of the high Ly alpha to X-ray luminosity ratio (L-Ly alpha/L-X approximate to 0.3, greater than or similar to 10-1000 times. higher than in local cool-core clusters) and by current modeling. Given the physical conditions of the Ly alpha-emitting gas and the possible interplay with the X-ray phase, we argue that the Ly alpha nebula would be short-lived (less than or similar to 10 Myr) if not continuously replenished with cold gas at a rate of greater than or similar to 1000 M-circle dot yr(-1). We investigate the possibility that cluster galaxies supply the required gas through outflows and we show that their total mass outflow rate matches the replenishment necessary to sustain the nebula. This scenario directly implies the extraction of energy from galaxies and its deposition in the surrounding intracluster medium (ICM), as required to explain the thermodynamic properties of local clusters. We estimate an energy injection of the order of approximate to 2 keV per particle in the ICM over a 2 Gyr interval. In our baseline calculation, AGNs provide up to 85% of the injected energy and two-thirds. of the mass, while the rest is supplied by supernovae-driven winds.
  • 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.
  • 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.
  • 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.
  • Aghanim, N.; Altieri, B.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Beelen, A.; Benabed, K.; Benoit-Levy, A.; Bernard, J. -P.; Bersanelli, M.; Bethermin, M.; Bielewicz, P.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Calabrese, E.; Canameras, R.; Cardoso, J. -F.; Catalano, A.; Chamballu, A.; Chary, R. -R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Crill, B. P.; Curto, A.; Danese, L.; Dassas, K.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Diego, J. M.; Dole, H.; Donzelli, S.; Keihänen, Elina; Kurki-Suonio, H.; Valiviita, J. (2015)
    We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353-857 GHz. This colour-selection favours galaxies in the redshift range z = 2-4, which we consider as cold peaks in the cosmic infrared background. With a 4.'5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500 mu m sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350 mu m, with 3% peaking at 500 mu m, and none peaking at 250 mu m. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z > 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10 sigma. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z similar or equal to 2, assuming a single common dust temperature for the sources of T-d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4x10(12) L-circle dot, yielding star formation rates of typically 700 M-circle dot yr(-1). If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 x 10(13) L-circle dot, leading to total star formation rates of perhaps 7 x 10(3) M-circle dot yr(-1) per overdensity. Taken together, these sources show the signatures of high-z (z > 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-sky Planck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.
  • Reeves, Andrew M. M.; Balogh, Michael L.; van der Burg, Remco F. J.; Finoguenov, Alexis; Kukstas, Egidijus; McCarthy, Ian G.; Webb, Kristi; Muzzin, Adam; McGee, Sean; Rudnick, Gregory; Biviano, Andrea; Cerulo, Pierluigi; Chan, Jeffrey C. C.; Cooper, M. C.; Demarco, Ricardo; Jablonka, Pascale; De Lucia, Gabriella; Vulcani, Benedetta; Wilson, Gillian; Yee, Howard K. C.; Zaritsky, Dennis (2021)
    We use photometric redshifts and statistical background subtraction to measure stellar mass functions in galaxy group-mass (4.5-8 x 10(13) M-circle dot) haloes at 1 < z < 1.5. Groups are selected from COSMOS and SXDF, based on X-ray imaging and sparse spectroscopy. Stellar mass (M-stell(ar)) functions are computed for quiescent and star-forming galaxies separately, based on their rest-frame UVJ colours. From these we compute the quiescent fraction and quiescent fraction excess (QFE) relative to the field as a function of M-stel(lar). QFE increases with M-st(ellar), similar to more massive clusters at 1 < z < 1.5. This contrasts with the apparent separability of M-stellar, and environmental factors on galaxy quiescent fractions at z similar to 0. We then compare our results with higher mass clusters at 1 < z < 1.5 and lower redshifts. We find a strong QFE dependence on halo mass at fixed M-ste(ll)ar; well fit by a logarithmic slope of d(QFE)/dlog (M-halo) similar to 0.24 +/- 0.04 for all M-stellar and redshift bins. This dependence is in remarkably good qualitative agreement with the hydrodynamic simulation BAHAMAS, but contradicts the observed dependence of QFE on M-stellar. We interpret the results using two toy models: one where a time delay until rapid (instantaneous) quenching begins upon accretion to the main progenitor ( 'no pre-processing') and one where it starts upon first becoming a satellite ('pre-processing'). Delay times appear to be halo mass-dependent, with a significantly stronger dependence required without pre-processing. We conclude that our results support models in which environmental quenching begins in low-mass ( 1.
  • McAlpine, Stuart; Smail, Ian; Bower, Richard G.; Swinbank, A. M.; Trayford, James W.; Theuns, Tom; Baes, Maarten; Camps, Peter; Crain, Robert A.; Schaye, Joop (2019)
    We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed submillimetre (submm) galaxy population by selecting the model galaxies at z >= 1 with mock submm fluxes S-850 mu m >= 1mJy. We find a reasonable agreement between the model galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at z <3, redshift distribution, and many integrated galaxy properties. We find that the median redshift of the S-850 (mu m) >= 1mJy model population is z approximate to 2.5, and that they are massive galaxies (M-* similar to 10(11)M(circle dot)) with high dust masses (M-dust similar to 10(8)M(circle dot)), gas fractions (f(gas) approximate to 50 per cent), and SFRs ((*) approximate to 100 M-circle dot yr(-1)). In addition, we find that they have major and minor merger fractions similar to the general population, suggesting that mergers are not the sole driver of the high SFRs in the model submm galaxies. Instead, the S-850 (mu m) >= 1mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole relative to comparably massive galaxies. Not all 'highly star-forming' ((*) >= 80M(circle dot) yr(-1)) EAGLE galaxies have submm fluxes S-850 (mu m) >= 1 mJy. We investigate the nature of these highly star-forming 'Submm-Faint' galaxies (i.e. (*) = 80 M-circle dot yr(-1) but S-850 (mu m) <1mJy) and find that they are similar to the model submm galaxies, being gas rich and hosting undermassive black holes. However, they are also typically at higher redshifts (z > 4) and are lower mass (M-* similar to 10(10) M-circle dot). These typically higher redshift galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by most current submm surveys due to their higher dust temperatures and lower dust masses.
  • 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.
  • Paolillo, M.; Papadakis, I.; Brandt, W. N.; Luo, B.; Xue, Y. Q.; Tozzi, P.; Shemmer, O.; Allevato, V.; Bauer, F. E.; Comastri, A.; Gilli, R.; Koekemoer, A. M.; Liu, T.; Vignali, C.; Vito, F.; Yang, G.; Wang, J. X.; Zheng, X. C. (2017)
    We study the X-ray variability properties of distant active galactic nuclei (AGNs) in the Chandra Deep Field-South region over 17 yr, up to z similar to 4, and compare them with those predicted by models based on local samples. We use the results of Monte Carlo simulations to account for the biases introduced by the discontinuous sampling and the low-count regime. We confirm that variability is a ubiquitous property of AGNs, with no clear dependence on the density of the environment. The variability properties of high-z AGNs, over different temporal time-scales, are most consistent with a power spectral density (PSD) described by a broken (or bending) power law, similar to nearby AGNs. We confirm the presence of an anticorrelation between luminosity and variability, resulting from the dependence of variability on black hole (BH) mass and accretion rate. We explore different models, finding that our acceptable solutions predict that BH mass influences the value of the PSD break frequency, while the lambda(Edd) ington ratio lambda(Edd) affects the PSD break frequency and, possibly, the PSD amplitude as well. We derive the evolution of the average.Edd as a function of redshift, finding results in agreement with measurements based on different estimators. The large statistical uncertainties make our results consistent with a constant Eddington ratio, although one of our models suggest a possible increase of lambda(Edd) with lookback time up to z similar to 2-3. We conclude that variability is a viable mean to trace the accretion history of supermassive BHs, whose usefulness will increase with future, wide-field/large effective area X-ray missions.