Browsing by Subject "infrared: galaxies"

Now showing 1 - 11 of 11
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    CO in Hickson compact group galaxies with enhanced warm H 2 emission: Evidence for galaxy evolution?
    (2014) Lisenfeld, U; Appleton, P N; Cluver, M E; Guillard, P; Alatalo, K; Ogle, P
    Context. Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H2 to the 7.7 μm PAH emission (so-called Molecular Hydrogen Emission Galaxies, MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H2 emission suggests that the molecular gas is affected in the transition.
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    Cosmological model dependence of the galaxy luminosity function: far-infrared results in the Lemaître-Tolman-Bondi model
    (2013) Iribarrem, A; Andreani, P; Gruppioni, C; February, S; Ribeiro, M B; Berta, S; Le Floc’h, E; Magnelli, B; Nordon, R; Popesso, P; Pozzi, F; Riguccini, L
    Aims. This is the first paper of a series aiming at investigating galaxy formation and evolution in the giant-void class of the Lemaître-Tolman-Bondi (LTB) models that best fits current cosmological observations. Here we investigate the luminosity function (LF) methodology, and how its estimates would be affected by a change on the cosmological model assumed in its computation. Are the current observational constraints on the allowed cosmology enough to yield robust LF results?
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    Deep Ks -near-infrared surface photometry of 80 dwarf irregular galaxies in the local volume
    (2010) Fingerhut, Robin L; McCall, Marshall L; Argote, Mauricio; Cluver, Michelle E; Nishiyama, Shogo; Rekola, Rami T F; Richer, Michael G; Vaduvescu, Ovidiu; Woudt, Patrick A
    We present deep near-infrared (K_s) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ~5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies.
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    Herschel observations of Hickson compact groups of galaxies: Unveiling the properties of cold dust
    (2014) Bitsakis, T; Charmandaris, V; Appleton, P N; Díaz-Santos, T; Le Floc’h, E; da Cunha, E; Alatalo, K; Cluver, M
    We present a Herschel far-IR and sub-mm study of a sample of 120 galaxies in 28 Hickson Compact Groups. Fitting their UV to sub-mm spectral energy distributions with the model of da Cunha et al. (2008), we accurately estimate the dust masses, luminosities and temperatures of the individual galaxies. We find that nearly half of the late-type galaxies in dynamically "old" groups, those with more than 25% of early-type members and redder UV-optical colours, have also significantly lower dust-to-stellar mass ratios compared to those of actively star-forming galaxies of the same mass found both in HCGs and the field. Examining their dust-to-gas mass ratios we conclude that dust was stripped out of these systems as a result of the gravitational and hydrodynamic interactions, experienced due to previous encounters with other group members. About 40% of the early-type galaxies (mostly lenticulars), in dynamically "old" groups, display dust properties similar to those of the UV-optical red late-type galaxies. Given their stellar masses, star formation rates and UV-optical colours, we suggest that red late-type and dusty lenticular galaxies represent transition populations between blue star-forming disk galaxies and quiescent early-type ellipticals. [...ABRIDGED...] Our deep Herschel observations also allow us to detect the presence of diffuse cold intragroup dust in 4 HCGs. We also find that the fraction of 250micron emission which is located outside of the main bodies of the red late-type galaxies as well as of the dusty lenticulars is 15-20% of their integrated emission at this band. All these findings are consistent with an evolutionary scenario in which gas dissipation, shocks and turbulence in addition to tidal interactions, shape the evolution of galaxies in compact groups.
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    H I line observations of 2MASS galaxies in the zoneof avoidance
    (2009) van Driel, W; Schneider, S E; Kraan-Korteweg, R C; Monnier Ragaigne, D
    A pilot survey has been made to obtain 21 cm H
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    Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)
    (2016) Duah Asabere, B; Horellou, C; Jarrett, T H; Winkler, H
    Context. Most radio galaxies are hosted by giant gas-poor ellipticals, but some contain significant amounts of dust, which is likely to be of external origin.
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    Overdensities of SMGs around WISE-selected, ultraluminous, high-redshift AGNs
    (2017) Jones, Suzy F; Blain, Andrew W; Assef, Roberto J; Eisenhardt, Peter; Lonsdale, Carol; Condon, James; Farrah, Duncan; Tsai, Chao-Wei; Bridge, Carrie; Wu, Jingwen; Wright, Edward L; Jarrett, Tom
    We investigate extremely luminous dusty galaxies in the environments around Wide-field Infrared Survey Explorer (WISE)-selected hot dust-obscured galaxies (Hot DOGs) and WISE/radio-selected active galactic nuclei (AGNs) at average redshifts of z = 2.7 and 1.7, respectively. Previous observations have detected overdensities of companion submillimetre-selected sources around 10 Hot DOGs and 30 WISE/radio AGNs, with overdensities of similar to 2-3 and similar to 5-6, respectively. We find that the space densities in both samples to be overdense compared to normal star-forming galaxies and submillimetre galaxies (SMGs) in the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) Cosmology Legacy Survey (S2CLS). Both samples of companion sources have consistent mid-infrared (mid-IR) colours and mid-IR to submm ratios as SMGs. The brighter population around WISE/radio AGNs could be responsible for the higher overdensity reported. We also find that the star formation rate densities are higher than the field, but consistent with clusters of dusty galaxies. WISE-selected AGNs appear to be good signposts for protoclusters at high redshift on arcmin scales. The results reported here provide an upper limit to the strength of angular clustering using the two-point correlation function. Monte Carlo simulations show no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5-arcmin scale maps.
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    Relativistic cosmology number densities in void-Lemaître-Tolman-Bondi models
    (2014) Iribarrem, A; Andreani, P; February, S; Gruppioni, C; Lopes, A R; Ribeiro, M B; Stoeger, W R
    Aims. The goal of this work is to compute the number density of far-IR selected galaxies in the comoving frame and along the past lightcone of observationally constrained Lemaître-Tolman-Bondi “giant void” models and to compare those results with their standard model counterparts.
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    Shock-enhanced C+ emission and the detection of H2O from the Stephan’s Quintet group-wide shock using Herschel
    (2013) Appleton, P N; Guillard, P; Boulanger, F; Cluver, M E; Ogle, P; Falgarone, E; Pineau des Forêts, G; O\'Sullivan, E; Duc, P-A; Gallagher, S; Gao, Y; Jarrett, T; Konstantopoulos, I; Lisenfeld, U; Lord, S; Lu, N; Peterson, B W; Struck, C; Sturm, E; Tuffs, R; Valchanov, I; van der Werf, P; Xu, K C
    WWe present the first Herschelspectroscopic detections of the [O i] 63 μm and [Cii] 158 μm fine-structure transitions, and a single para-H2O line from the 35 × 15 kpc2 shocked intergalactic filament in Stephan’s Quintet. The filament is believed to have been formed when a high-speed intruder to the group collided with a clumpy intergroup gas. Observations with the PACS spectrometer provide evidence for broad (>1000 km s−1) luminous [Cii] line profiles, as well as fainter [O i] 63 μm emission. SPIRE FTS observations reveal water emission from the p-H2O (111–000) transition at several positions in the filament, but no other molecular lines. The H2O line is narrow and may be associated with denser intermediate-velocity gas experiencing the strongest shock-heating. The [Cii]/PAHtot and [C ii]/FIR ratios are too large to be explained by normal photo-electric heating in photodissociation regions. H ii region excitation or X-ray/cosmic-ray heating can also be ruled out. The observations lead to the conclusion that a large fraction the molecular gas is diffuse and warm. We propose that the [Cii], [O i], and warm H2 line emission is powered by a turbulent cascade in which kinetic energy from the galaxy collision with the intergalactic medium is dissipated to small scales and low velocities, via shocks and turbulent eddies. Low-velocity magnetic shocks can help explain both the [Cii]/[O i] ratio, and the relatively high [C ii]/H2 ratios observed. The discovery that [Cii] emission can be enhanced, in large-scale turbulent regions in collisional environments, has implications for the interpretation of [C ii] emission in high-z galaxies.
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    UV-BRIGHT NEARBY EARLY-TYPE GALAXIES OBSERVED IN THE MID-INFRARED: EVIDENCE FOR A MULTI-STAGE FORMATION HISTORY BY WAY OF WISE AND GALEX IMAGING
    (2013) Petty, S M; Neill, J D; Jarrett, T H; Blain, A W; Farrah, D G; Rich, R M; Tsai, C W; Benford, D J; Bridge, C R; Lake, S E; Masci, F J; Wright, E L
    In the local Universe, 10% of massive elliptical galaxies are observed to exhibit a peculiar property: a substantial excess of ultraviolet emission (UVX) over what is expected from their old, red stellar populations. Several origins for the UVX have been proposed, including a population of hot young stars, or a population of old, blue horizontal branch or extended horizontal branch (BHB or EHB) stars that have undergone substantial mass loss from their outer atmospheres. We explore the radial distribution of ultraviolet excess (UVX) in a selection of 49 nearby E/S0-type galaxies by measuring the extended photometry in the UV-midIR with GALEX, SDSS and WISE. We compare UV/optical and UV/mid-IR colors with the Flexible Stellar Population Synthesis with EHB models (Conroy & Gunn 2010). We find that combined WISE mid-IR and GALEX UV colors are more effective in distinguishing models than optical colors, and that the UV/mid-IR combination is sensitive to EHB fraction. There are strong color gradients with the outer radii bluer than the inner half-light radii by ~1 magnitude. This color difference is easily accounted for with a BHB fraction increase of 0.25 with radius. We estimated the average ages for the inner and outer radii are 7.0+/-0.3 Gyr, and 6.2+/-0.2 Gyr, respectively, with the implication that the outer regions are likely to have formed ~1 Gyr after the inner regions. Additionally, we find that metallicity gradients are likely not a significant factor in the color difference. The separation of color between the inner and outer regions, which agrees with a specific stellar population difference (e.g., higher EHB populations), and the ~0.5-2 Gyr age difference suggests multi-stage formation. Our results are best explained by inside-out formation: rapid star formation within the core at early epochs (>4 Gyr ago) and at least one later stage starburst event coinciding with z~1
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    Wise detections of known QSOs at redshifts greater than six
    (2013) Blain, Andrew W; Assef, Roberto; Stern, Daniel; Tsai, Chao-Wei; Eisenhardt, Peter; Bridge, Carrie; Benford, Dominic; Jarrett, Tom; Cutri, Roc; Petty, Sara; Wu, Jingwen; Wright, Edward L
    We present WISE All-Sky mid-infrared (IR) survey detections of 55% (17/31) of the known QSOs at z > 6 from a range of surveys: the SDSS, the CFHT-LS, FIRST, Spitzer, and UKIDSS. The WISE catalog thus provides a substantial increase in the quantity of IR data available for these sources: 17 are detected in the WISE W1 (3.4 mu m) band, 16 in W2 (4.6 mu m), 3 in W3 (12 mu m), and 0 in W4 (22 mu m). This is particularly important with Spitzer in its warm-mission phase and no faint follow-up capability at wavelengths longward of 5 mu m until the launch of James Webb Space Telescope (JWST). WISE thus provides a useful tool for understanding QSOs found in forthcoming large-area optical/IR sky surveys using PanSTARRS, SkyMapper, VISTA, DES, and LSST. The rest-UV properties of the WISE-detected and the WISE-non-detected samples differ: the detections have brighter i/z-band magnitudes and redder rest-UV colors. This suggests that a more aggressive hunt for very high redshift QSOs by combining WISE W1 and W2 data with red, observed optical colors could be effective at least for a subset of dusty candidate QSOs. Stacking the WISE images of the WISE-non-detected QSOs indicates that they are, on average, significantly fainter than the WISE-detected examples, and are thus not narrowly missing detection in the WISE catalog. The WISE catalog detection of three of our sample in the W3 band indicates that their mid-IR flux can be detected individually, although there is no stacked W3 detection of sources detected in W1 but not W3. Stacking analyses of WISE data for large active galactic nucleus samples will be a useful tool, and high-redshift QSOs of all types will be easy targets for JWST.