Browsing by Subject "ACTIVE GALACTIC NUCLEI"

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  • Vardoulaki, E.; Andrade, E. F. Jimenez; Karim, A.; Novak, M.; Leslie, S. K.; Tisanic, K.; Smolcic, V.; Schinnerer, E.; Sargent, M. T.; Bondi, M.; Zamorani, G.; Magnelli, B.; Bertoldi, F.; Ruiz, N. Herrera; Mooley, K. P.; Delhaize, J.; Myers, S. T.; Marchesi, S.; Koekemoer, A. M.; Gozaliasl, G.; Finoguenov, A.; Middleberg, E.; Ciliegi, P. (2019)
    Context. Given the unprecedented depth achieved in current large radio surveys, we are starting to probe populations of radio sources that have not been studied in the past. However, identifying and categorising these objects, differing in size, shape and physical properties, is becoming a more difficult task. Aims. In this data paper we present and characterise the multi-component radio sources identified in the VLA-COSMOS Large Project at 3 GHz (0.75 arcsec resolution, 2.3 mu Jy beam(-1) rms), i.e. the radio sources which are composed of two or more radio blobs. Methods. The classification of objects into multi-components was done by visual inspection of 351 of the brightest and most extended blobs from a sample of 10,899 blobs identified by the automatic code BLOBCAT. For that purpose we used multi-wavelength information of the field, such as the 1.4 GHz VLA-COSMOS data and the Ultra Deep Survey with the VISTA telescope (UltraVISTA) stacked mosaic available for COSMOS. Results. We have identified 67 multi-component radio sources at 3 GHz: 58 sources with active galactic nucleus (AGN) powered radio emission and nine star-forming galaxies. We report eight new detections that were not observed by the VLA-COSMOS Large Project at 1.4 GHz, due to the slightly larger area coverage at 3 GHz. The increased spatial resolution of 0.75 arcsec has allowed us to resolve (and isolate) multiple emission peaks of 28 extended radio sources not identified in the 1.4 GHz VLA-COSMOS map. We report the multi-frequency flux densities (324 MHz, 325 MHz, 1.4 GHz & 3 GHz), star formation rates, and stellar masses of these objects. We find that multi-component objects at 3 GHz VLA-COSMOS inhabit mainly massive galaxies (>10(10.5)M(circle dot)). The majority of the multi-component AGN lie below the main sequence of star-forming galaxies (SFGs), in the green valley and the quiescent region. Furthermore, we provide detailed descriptions of the objects and find that amongst the AGN there are two head-tail, ten corelobe, nine wide-angle-tail (WAT), eight double-double or Z-/X-shaped, three bent-tail radio sources, and 26 symmetric sources, while amongst the SFGs we find the only star-forming ring seen in radio emission in COSMOS. Additionally, we report a large number (32 out of 58) of disturbed/bent multi-component AGN, 18 of which do not lie within X-ray groups in COSMOS (redshift range 0.08 Conclusion. The high angular resolution and sensitivity of the 3 GHz VLA-COSMOS data set give us the opportunity to identify peculiar radio structures and sub-structures of multi-component objects, and relate them to physical phenomena such as AGN or star-forming galaxies. This study illustrates the complexity of the mu Jy radio-source population; at the sensitivity and resolution of 3 GHz VLA-COSMOS, the radio structures of AGN and SFG both emitting radio continuum emission, become comparable in the absence of clear, symmetrical jets. Thus, disentangling the AGN and SFG contributions using solely radio observations can be misleading in a number of cases. This has implications for future surveys, such as those done by square kilometre array (SKA) and precursors, which will identify hundreds of thousands of multi-component objects.
  • 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.
  • Valtonen, Mauri J.; Zola, Staszek; Pihajoki, Pauli; Enestam, Sissi; Lehto, Harry J.; Dey, Lankeswar; Gopakumar, Achamveedu; Drozdz, Marek; Ogloza, Waldemar; Zejmos, Michal; Gupta, Alok C.; Pursimo, Tapio; Ciprini, Stefano; Kidger, Mark; Nilsson, Kari; Berdyugin, Andrei; Piirola, Vilppu; Jermak, Helen; Hudec, Rene; Laine, Seppo (2019)
    In the binary black hole model of OJ. 287, the secondary black hole orbits a much more massive primary, and impacts on the primary accretion disk at predictable times. We update the parameters of the disk, the viscosity, alpha, and the mass accretion rate, . We find alpha = 0.26 +/- 0.1 and = 0.08 +/- 0.04 in Eddington units. The former value is consistent with Coroniti, and the latter with Marscher & Jorstad. Predictions are made for the 2019 July 30 superflare in OJ. 287. We expect that it will take place simultaneously at the Spitzer infrared channels, as well as in the optical, and that therefore the timing of the flare in optical can be accurately determined from Spitzer observations. We also discuss in detail the light curve of the 2015 flare, and find that the radiating volume has regions where bremsstrahlung dominates, as well as regions that radiate primarily in synchrotron radiation. The former region produces the unpolarized first flare, while the latter region gives rise to a highly polarized second flare.
  • Mirkazemi, M.; Finoguenov, A.; Pereira, M. J.; Tanaka, M.; Lerchster, M.; Brimioulle, F.; Egami, E.; Kettula, K.; Erfanianfar, G.; McCracken, H. J.; Mellier, Y.; Kneib, J. P.; Rykoff, E.; Seitz, S.; Erben, T.; Taylor, J. E. (2015)
  • 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.
  • 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
  • Georgakakis, A.; Comparat, J.; Merloni, A.; Ciesla, L.; Aird, J.; Finoguenov, A. (2019)
    A semi-empirical model is presented that describes the distribution of active galactic nuclei (AGNs) on the cosmicweb. It populates dark-matter haloes in N-body simulations (MultiDark) with galaxy stellar masses using empirical relations based on abundance matching techniques, and then paints accretion events on these galaxies using state-of-the-art measurements of the AGN occupation of galaxies. The explicit assumption is that the large-scale distribution of AGN is independent of the physics of black hole fuelling. The model is shown to be consistent with current measurements of the two-point correlation function of AGN samples. It is then used to make inferences on the halo occupation of the AGN population. Mock AGNs are found in haloes with a broad distribution of masses with a mode of approximate to 10(12) h(-1) M-circle dot and a tail extending to cluster-size haloes. The clustering properties of the model AGN depend only weakly on accretion luminosity and redshift. The fraction of satellite AGN in the model increases steeply toward more massive haloes, in contrast with some recent observational results. This discrepancy, if confirmed, could point to a dependence of the halo occupation of AGN on the physics of black hole fuelling.
  • 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.
  • Vardoulaki, E.; Jimenez Andrade, E. F.; Delvecchio, I.; Zagreb, University; Schinnerer, E.; Sargent, M. T.; Gozaliasl, G.; Finoguenov, A.; Bondi, M.; Zamorani, G.; Badescu, T.; Leslie, S. K.; Ceraj, L.; Tisanic, K.; Karim, A.; Magnelli, B.; Bertoldi, F.; Romano-Diaz, E.; Harrington, K. (2021)
    Context. Radio active galactic nuclei (AGN) are traditionally separated into two Fanaroff-Riley (FR) type classes, edge-brightened FRII sources or edge-darkened FRI sources. With the discovery of a plethora of radio AGN of different radio shapes, this dichotomy is becoming too simplistic in linking the radio structure to the physical properties of radio AGN, their hosts, and their environment.Aims. We probe the physical properties and large-scale environment of radio AGN in the faintest FR population to date, and link them to their radio structure. We use the VLA-COSMOS Large Project at 3 GHz (3 GHz VLA-COSMOS), with a resolution and sensitivity of 75 0 75 and 2.3 mu Jy beam(-1) to explore the FR dichotomy down to mu Jy levels.Methods. We classified objects as FRIs, FRIIs, or hybrid FRI/FRII based on the surface-brightness distribution along their radio structure. Our control sample was the jet-less/compact radio AGN objects (COM AGN), which show excess radio emission at 3 GHz VLA-COSMOS exceeding what is coming from star-formation alone; this sample excludes FRs. The largest angular projected sizes of FR objects were measured by a machine-learning algorithm and also by hand, following a parametric approach to the FR classification. Eddington ratios were calculated using scaling relations from the X-rays, and we included the jet power by using radio luminosity as a probe. Furthermore, we investigated their host properties (star-formation ratio, stellar mass, morphology), and we explore their incidence within X-ray galaxy groups in COSMOS, and in the density fields and cosmic-web probes in COSMOS.Results. Our sample is composed of 59 FRIIs, 32 FRI/FRIIs, 39 FRIs, and 1818 COM AGN at 0.03 (238.2)(36.9) 36.9 238.2 kpc, larger than that of FRI/FRIIs and FRIs by a factor of 2-3. The COM AGN have sizes smaller than 30 kpc, with a median value of 1.7 (4.7)(1.5) 1.5 4.7 kpc. The median Eddington ratio of FRIIs is 0.006 (0.007)(0.005) 0.005 0.007 , a factor of 2.5 less than in FRIs and a factor of 2 higher than in FRI/FRII. When the jet power is included, the median Eddington ratios of FRII and FRI/FRII increase by a factor of 12 and 15, respectively. FRs reside in their majority in massive quenched hosts (M-*>10(10.5) M-circle dot), with older episodes of star-formation linked to lower X-ray galaxy group temperatures, suggesting radio-mode AGN quenching. Regardless of their radio structure, FRs and COM AGN are found in all types and density environments (group or cluster, filaments, field).Conclusions. By relating the radio structure to radio luminosity, size, Eddington ratio, and large-scale environment, we find a broad distribution and overlap of FR and COM AGN populations. We discuss the need for a different classification scheme, that expands the classic FR classification by taking into consideration the physical properties of the objects rather than their projected radio structure which is frequency-, sensitivity- and resolution-dependent. This point is crucial in the advent of current and future all-sky radio surveys.
  • 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.
  • 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.
  • Pinto, C.; Fabian, A. C.; Ogorzalek, A.; Zhuravleva, I.; Werner, N.; Sanders, J.; Zhang, Y. -Y.; Gu, Liyi; de Plaa, J.; Ahoranta, J.; Finoguenov, A.; Johnstone, R.; Canning, R. E. A. (2016)
    We extend our previous study of the cool gas responsible for the emission of O VII X-ray lines in the cores of clusters and groups of galaxies. This is the coolest X-ray emitting phase and connects the 10 000 K H alpha emitting gas to the million degree phase, providing a useful tool to understand cooling in these objects. We study the location of the O VII gas and its connection to the intermediate Fe XVII and hotter O VIII phases. We use high-resolution X-ray grating spectra of elliptical galaxies with strong Fe XVII line emission and detect O VII in 11 of 24 objects. Comparing the O VII detection level and resonant scattering, which is sensitive to turbulence and temperature, suggests that O VII is preferably found in cooler objects, where the Fe XVII resonant line is suppressed due to resonant scattering, indicating subsonic turbulence. Although a larger sample of sources and further observations is needed to distinguish between effects from temperature and turbulence, our results are consistent with cooling being suppressed at high turbulence as predicted by models of active galactic nuclei feedback, gas sloshing and galactic mergers. In some objects, the O VII resonant-to-forbidden line ratio is decreased by either resonant scattering or charge exchange boosting the forbidden line, as we show for NGC 4636. Charge exchange indicates interaction between neutral and ionized gas phases. The Perseus cluster also shows a high Fe XVII forbidden-to-resonance line ratio, which can be explained with resonant scattering by low-turbulence cool gas in the line of sight.
  • Zhoolideh Haghighi, Mohammad H.; Raouf, Mojtaba; Khosroshahi, Habib. G.; Farhang, Amin; Gozaliasl, Ghassem (2020)
    We characterize the relaxation state of galaxy systems by providing an assessment of the reliability of the photometric and spectroscopic probe via the semianalytic galaxy evolution model. We quantify the correlations between the dynamical age of simuglated galaxy groups and popular proxies of halo relaxation in observation, which are mainly either spectroscopic or photometric. We find the photometric indicators demonstrate a stronger correlation with the dynamical relaxation of galaxy groups compared to the spectroscopic probes. We take advantage of the Anderson Darling statistic (A(2)) and the velocity segregation (Delta V) as our spectroscopic indicators, and use the luminosity gap (Delta m(12)) and the luminosity decentering (D-offset) as photometric ones. First, we find that a combination of Delta m(12) and D-offset evaluated by a bivariant relation (B = 0.04 x Delta m(12) - 0.11 x Log(Doff-set) + 0.28) shows a good correlation with the dynamical age compared to all other indicators. Second, by using the observational X-ray surface brightness map, we show that the bivariant relation brings about some acceptable correlations with X-ray proxies. These correlations are as well as the correlations between A(2) and X-ray proxies, offering a reliable yet fast and economical method of quantifying the relaxation of galaxy systems. This study demonstrates that using photometric data to determine the relaxation status of a group will lead to some promising results that are comparable with the more expensive spectroscopic counterpart.
  • Ade, P. A. R.; Juvela, M.; Keihanen, E.; Kurki-Suonio, H.; Poutanen, T.; Suur-Uski, A. -S.; Planck Collaboration (2013)
  • 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.
  • Shankar, Francesco; Bernardi, Mariangela; Sheth, Ravi K.; Ferrarese, Laura; Graham, Alister W.; Savorgnan, Giulia; Allevato, Viola; Marconi, Alessandro; Läsker, Ronald; Lapi, Andrea (2016)
    We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample of galaxies extracted from the Sloan Digital Sky Survey. We confirm earlier work showing that the majority of black hole hosts have significantly higher velocity dispersions sigma than local galaxies of similar stellar mass. We use Monte Carlo simulations to illustrate the effect on black hole scaling relations if this bias arises from the requirement that the black hole sphere of influence must be resolved to measure black hole masses with spatially resolved kinematics. We find that this selection effect artificially increases the normalization of the M-bh-sigma relation by a factor of at least similar to 3; the bias for the M-bh-M-star relation is even larger. Our Monte Carlo simulations and analysis of the residuals from scaling relations both indicate that sigma is more fundamental than M-star or effective radius. In particular, the M-bh-M-star relation is mostly a consequence of the M-bh-sigma and sigma-M-star relations, and is heavily biased by up to a factor of 50 at small masses. This helps resolve the discrepancy between dynamically based black hole-galaxy scaling relations versus those of active galaxies. Our simulations also disfavour broad distributions of black hole masses at fixed sigma. Correcting for this bias suggests that the calibration factor used to estimate black hole masses in active galaxies should be reduced to values of f(vir) similar to 1. Black hole mass densities should also be proportionally smaller, perhaps implying significantly higher radiative efficiencies/black hole spins. Reducing black hole masses also reduces the gravitational wave signal expected from black hole mergers.
  • Väisänen, Petri; Reunanen, Juha; Kotilainen, Jari; Mattila, Seppo; Johansson, Peter H.; Ramphul, Rajin; Romero-Canizales, Cristina; Kuncarayakti, Hanindyo (2017)
    We present new SINFONI near-infrared (NIR) integral field unit (IFU) spectroscopy and Southern African Large Telescope (SALT) optical long-slit spectroscopy characterizing the history of a nearby merging luminous infrared galaxy, dubbed the Bird (IRAS19115-2124). TheNIR line-ratio maps of the IFU data cubes and stellar population fitting of the SALT spectra now allow dating of the star formation (SF) over the triple system uncovered from our previous adaptive optics data. The distinct components separate clearly in line-ratio diagnostic diagrams, both thermal and non-thermal excitation is present. An off-nuclear starburst dominates the current SF of the Bird with 60-70 per cent of the total, with a 4-7 Myr age. The most massive nucleus, in contrast, is quenched with a starburst age of >40 Myr and shows hints of budding active galactic nucleus (AGN) activity. The secondary massive nucleus is at an intermediate stage. The two major components have signs of an older stellar population, consistent with a starburst triggered 1 Gyr ago in a first encounter. The simplest explanation of the history is that of a triple merger, where the strongly star-forming component has joined later. We detect multiple gas flows. The Bird offers an opportunity to witness multiple stages of galaxy evolution in the same system; triggering as well as very recent quenching of SF, and, perhaps, an early appearance of AGN activity. It also serves as a cautionary note on interpretations of observations with lower spatial resolution and/or without infrared data. At high redshift the system would look like a clumpy starburst with crucial pieces of its puzzle hidden in danger of misinterpretations.
  • Habouzit, Melanie; Li, Yuan; Somerville, Rachel S.; Genel, Shy; Pillepich, Annalisa; Volonteri, Marta; Dave, Romeel; Rosas-Guevara, Yetli; McAlpine, Stuart; Peirani, Sebastien; Hernquist, Lars; Anglés-Alcázar, Daniel; Reines, Amy; Bower, Richard; Dubois, Yohan; Nelson, Dylan; Pichon, Christophe; Vogelsberger, Mark (2021)
    The past decade has seen significant progress in understanding galaxy formation and evolution using large-scale cosmological simulations. While these simulations produce galaxies in overall good agreement with observations, they employ different sub-grid models for galaxies and supermassive black holes (BHs). We investigate the impact of the sub-grid models on the BH mass properties of the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA simulations, focusing on the M-BH - M-star relation and the BH mass function. All simulations predict tight M-BH - M-star relations, and struggle to produce BHs of M-BH = 109M (circle dot) in most of the simulations. The BH mass function is dominated by efficiently accreting BHs ((log(10) f(Edd) >= -2) at high redshifts, and transitions progressively from the high-mass to the low-mass end to be governed by inactive BHs. The transition time and the contribution of active BHs are different among the simulations, and can be used to evaluate models against observations.
  • Allevato, V.; Civano, F.; Finoguenov, A.; Marchesi, S.; Shankar, F.; Zamorani, G.; Hasinger, G.; Salvato, M.; Miyaji, T.; Gilli, R.; Cappelluti, N.; Brusa, M.; Suh, H.; Lanzuisi, G.; Trakhtenbrot, B.; Griffiths, R.; Vignali, C.; Schawinski, K.; Karim, A. (2016)
    We present the measurement of the projected and redshift-space two-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy active galactic nucleus (AGN) at 2.9 similar to 10(46) erg s(-1)) using the generalized clustering estimator based on phot-z probability distribution functions in addition to any available spec-z. We model the projected 2pcf, estimated using pi(max) = 200 h(-1) Mpc with the two-halo term and we derive a bias at z similar to 3.4 equal to b. =. 6.6(+0.60) -(0.55), which corresponds to a typical mass of the hosting halos of log M-h. =. 12.83(+0.12) -(0.11) h(-1)M circle dot. A similar bias is derived using the redshift-space 2pcf, modeled including the typical phot-z error sigma(z). =. 0.052 of our sample at z >= 2.9. Once we integrate the projected 2pcf up to pi(max). =. 200 h(-1) Mpc, the bias of XMM and Chandra COSMOS at z =. 2.8 used in Allevato et al. is consistent with our results at higher redshifts. The results suggest only a slight increase of the bias factor of COSMOS AGNs at z greater than or similar to 3 with the typical hosting halo mass of moderate-luminosity AGNs almost constant with redshift and equal to log M-h = 12.92(+0.-13) (0.18) at z - 2.8 and log M-h - 12.83(+0.11) (-0.12) at z similar to 3.4, respectively. The observed redshift evolution of the bias of COSMOS AGNs implies that moderate-luminosity AGNs. still inhabit group-sized halos at z greater than or similar to 3, but slightly less massive than observed in different independent studies using X-ray AGNs. at z less than or similar to 2.
  • Cappelluti, Nico; Li, Yanxia; Ricarte, Angelo; Agarwal, Bhaskar; Allevato, Viola; Ananna, Tonima Tasnim; Ajello, Marco; Civano, Francesca; Comastri, Andrea; Elvis, Martin; Finoguenov, Alexis; Gilli, Roberto; Hasinger, Guenther; Marchesi, Stefano; Natarajan, Priyamvada; Pacucci, Fabio; Treister, E.; Urry, C. Megan (2017)
    Using Chandra observations in the 2.15 deg(2) COSMOS-legacy field, we present one of the most accurate measurements of the Cosmic X-ray Background (CXB) spectrum to date in the [0.3-7] keV energy band. The CXB has three distinct components: contributions from two Galactic collisional thermal plasmas at kT similar to 0.27 and 0.07 keV and an extragalactic power law with a photon spectral index Gamma = 1.45 +/- 0.02. The 1 keV normalization of the extragalactic component is 10.91 +/- 0.16 keV cm(-2) s(-1) sr(-1) keV(-1). Removing all X-ray-detected sources, the remaining unresolved CXB is best fit by a power law with normalization 4.18 +/- 0.26 keV cm(-2) s(-1) sr(-1) keV(-1) and photon spectral index Gamma = 1.57 +/- 0.10. Removing faint galaxies down to i(AB) similar to 27-28 leaves a hard spectrum with Gamma similar to 1.25 and a 1 keV normalization of similar to 1.37 keV cm(-2) s(-1) sr(-1) keV(-1). This means that similar to 91% of the observed CXB is resolved into detected X-ray sources and undetected galaxies. Unresolved sources that contribute similar to 8%-9% of the total CXB show marginal evidence of being harder and possibly more obscured than resolved sources. Another similar to 1% of the CXB can be attributed to still undetected star-forming galaxies and absorbed active galactic nuclei. According to these limits, we investigate a scenario where early black holes totally account for non-source CXB fraction and constrain some of their properties. In order to not exceed the remaining CXB and the z similar to 6 accreted mass density, such a population of black holes must grow in Compton-thick envelopes with N-H > 1.6 x 10(25) cm(-2) and form in extremely low-metallicity environments (Z(circle dot)) similar to 10(-3).