P. Temi

NASA, Вашингтон, West Virginia, United States

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Publications (149)440.64 Total impact

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    ABSTRACT: Chaotic cold accretion (CCA) profoundly differs from classic black hole accretion models. Using 3D high-resolution simulations, we probe the impact of rotation on the hot and cold accretion flow in a typical massive galaxy. In the hot mode, with or without turbulence, the pressure-dominated flow forms a geometrically thick rotational barrier, suppressing the accretion rate to ~1/3 of the Bondi rate. When radiative cooling is dominant, the gas loses pressure support and quickly circularizes in a cold thin disk. In the more common state of a turbulent and heated atmosphere, CCA drives the dynamics if the gas velocity dispersion exceeds the rotational velocity, i.e., turbulent Taylor number < 1. Extended multiphase filaments condense out of the hot phase via thermal instability and rain toward the black hole, boosting the accretion rate up to 100 times the Bondi rate. Initially, turbulence broadens the angular momentum distribution of the hot gas, allowing the cold phase to condense with prograde or retrograde motion. Subsequent chaotic collisions between the cold filaments, clouds, and a clumpy variable torus promote the cancellation of angular momentum, leading to high accretion rates. The simulated sub-Eddington accretion rates cover the range inferred from AGN cavity observations. CCA predicts inner flat X-ray temperature and r^{−1} density profiles, as recently discovered in M 87 and NGC 3115. The synthetic H{\alpha} images reproduce the main features of cold gas observations in massive ellipticals, as the line fluxes and the filaments versus disk morphology. Such dichotomy is key for the long-term AGN feedback cycle. As gas cools, filamentary CCA develops and boosts AGN heating; the cold mode is thus reduced and the rotating disk remains the sole cold structure. Its consumption leaves the atmosphere in hot mode with suppressed accretion and feedback, reloading the cycle.
    Astronomy and Astrophysics 06/2015; 579(A62):18. DOI:10.1051/0004-6361/201526151
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    ABSTRACT: In this work we present IRAM-30m telescope observations of a sample of bulge-dominated galaxies with large dust lanes, which have had a recent minor merger. We find these galaxies are very gas rich, with H2 masses between 4x10^8 and 2x10^10 Msun. We use these molecular gas masses, combined with atomic gas masses from an accompanying paper, to calculate gas-to-dust and gas-to-stellar mass ratios. The gas-to-dust ratios of our sample objects vary widely (between ~50 and 750), suggesting many objects have low gas-phase metallicities, and thus that the gas has been accreted through a recent merger with a lower mass companion. We calculate the implied minor companion masses and gas fractions, finding a median predicted stellar mass ratio of ~40:1. The minor companion likely had masses between ~10^7 - 10^10 Msun. The implied merger mass ratios are consistent with the expectation for low redshift gas-rich mergers from simulations. We then go on to present evidence that (no matter which star-formation rate indicator is used) our sample objects have very low star-formation efficiencies (star-formation rate per unit gas mass), lower even than the early-type galaxies from ATLAS3D which already show a suppression. This suggests that minor mergers can actually suppress star-formation activity. We discuss mechanisms that could cause such a suppression, include dynamical effects induced by the minor merger.
    Monthly Notices of the Royal Astronomical Society 03/2015; 449(4). DOI:10.1093/mnras/stv597
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    ABSTRACT: Expanding X-ray cavities observed in hot gas atmospheres of many galaxy groups and clusters generate shock waves and turbulence that are primary heating mechanisms required to avoid uninhibited radiatively cooling flows which are not observed. However, we show here that the evolution of buoyant cavities also stimulates radiative cooling of observable masses of low-temperature gas. During their early evolution, radiative cooling occurs in the wakes of buoyant cavities in two locations: in thin radial filaments parallel to the buoyant velocity and more broadly in gas compressed beneath rising cavities. Radiation from these sustained compressions removes entropy from the hot gas. Gas experiencing the largest entropy loss cools first, followed by gas with progressively less entropy loss. Most cooling occurs at late times, $\sim 10^8-10^9$ yrs, long after the X-ray cavities have disrupted and are impossible to detect. During these late times, slightly denser low entropy gas sinks slowly toward the centers of the hot atmospheres where it cools intermittently, forming clouds near the cluster center. Single cavities of energy $10^{57}-10^{58}$ ergs in the atmosphere of the NGC 5044 group create $10^8 - 10^9$ $M_{\odot}$ of cooled gas, exceeding the mass of extended molecular gas currently observed in that group. The cooled gas clouds we compute share many attributes with molecular clouds recently observed in NGC 5044 with ALMA: self-gravitationally unbound, dust-free, quasi-randomly distributed within a few kpc around the group center.
    The Astrophysical Journal 01/2015; 802(2). DOI:10.1088/0004-637X/802/2/118
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    ABSTRACT: We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 ensuremath< ensuremath zensuremath<?iensuremath> ensuremath< 6 and absolute ensuremath Iensuremath<?iensuremath>-band magnitudes -22 ensuremath> ensuremath Iensuremath<?iensuremath>ensuremath ABensuremath<?subensuremath> ensuremath> -32 We use the science demonstration observations of the first textttchar12616 degensuremath 2ensuremath<?supensuremath> from the ensuremath Herschelensuremath<?iensuremath> Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, ensuremath Spitzerensuremath<?iensuremath>, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at ensuremath>5ensuremath ensuremathsigmaensuremath<?iensuremath> at 250,350 and 500 ensuremath ensuremathmuensuremath<?iensuremath>m. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 ensuremath> ensuremath Iensuremath<?iensuremath>ensuremath ABensuremath<?subensuremath> ensuremath> -24 have a comoving star formation rate (derived from 100 ensuremath ensuremathmuensuremath<?iensuremath>m rest-frame luminosities) peaking between redshifts of ensuremath 1ensuremath<?iensuremath> and ensuremath 2ensuremath<?iensuremath>, while high-luminosity quasars with ensuremath Iensuremath<?iensuremath>ensuremath ABensuremath<?subensuremath> ensuremath< -26 have a maximum contribution to the star formation density at ensuremath zensuremath<?iensuremath> textttchar126 3. The volume-averaged star formation rate of -22 ensuremath> ensuremath Iensuremath<?iensuremath>ensuremath ABensuremath<?subensuremath> ensuremath> -24 quasars evolves as (1 ? ensuremath zensuremath<?iensuremath>)ensuremath 2.3$pm$0.7ensuremath<?supensuremath> at ensuremath zensuremath<?iensuremath> ensuremath< 2, but the evolution at higher luminosities is much faster reaching (1 ? ensuremath zensuremath<?iensuremath>)ensuremath 10$pm$1ensuremath<?supensuremath> at -26 ensuremath> ensuremath Iensuremath<?iensuremath>ensuremath ABensuremath<?subensuremath> ensuremath> -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation.
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    ABSTRACT: The Stratospheric Observatory for Infrared Astronomy (SOFIA) is the world’s largest airborne observatory, featuring a 2.5 meter effective aperture telescope housed in the aft section of a Boeing 747SP aircraft. SOFIA’s current instrument suite includes: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), a 5-40 μm dual band imager/grism spectrometer developed at Cornell University; HIPO (High-speed Imaging Photometer for Occultations), a 0.3-1.1μm imager built by Lowell Observatory; GREAT (German Receiver for Astronomy at Terahertz Frequencies), a multichannel heterodyne spectrometer from 60-240 μm, developed by a consortium led by the Max Planck Institute for Radio Astronomy; FLITECAM (First Light Infrared Test Experiment CAMera), a 1-5 μm wide-field imager/grism spectrometer developed at UCLA; FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), a 42-200 μm IFU grating spectrograph completed by University Stuttgart; and EXES (Echelon-Cross-Echelle Spectrograph), a 5-28 μm highresolution spectrometer designed at the University of Texas and being completed by UC Davis and NASA Ames Research Center. HAWC+ (High-resolution Airborne Wideband Camera) is a 50-240 μm imager that was originally developed at the University of Chicago as a first-generation instrument (HAWC), and is being upgraded at JPL to add polarimetry and new detectors developed at Goddard Space Flight Center (GSFC). SOFIA will continually update its instrument suite with new instrumentation, technology demonstration experiments and upgrades to the existing instrument suite. This paper details the current instrument capabilities and status, as well as the plans for future instrumentation.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: A short 30 minute ALMA observation of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow, has detected 24 molecular structures within the central 2.5 kpc. The masses of the molecular structures vary from 3e5 to 1e7 Mo3 and the CO(2-1) linewidths vary from 15 to 65 km/s. Given the large CO(2-1) linewidths, the observed structures are likely giant molecular associations (GMAs) and not individual molecular clouds (GMCs). Only a few of the GMAs are spatially resolved with the cycle 0 ALMA beam and the average density of these GMAs yields a GMC volume filling factor of about 15%. The observed masses of the resolved GMAs are insufficient for them to be gravitationally bound, however, the most massive GMA does contain a less massive component with a linewidth of 5.5 km/s (typical of an individual virialized GMC). We also show that the GMAs cannot be pressure confined by the hot gas. Given the observed CO(2-1) linewidths of the GMAs (i.e., the velocity dispersion of the embedded GMCs) they will likely disperse on a timescale of about 12 Myr, which is less than the central cooling time of the hot gas, so the embedded GMCs within a GMA must condense out of the hot gas at the same time and arise from local concentrations of thermally unstable parcels of hot gas. There are no indications of any disk-like molecular structures and all indications suggest that the molecular gas follows ballistic trajectories after condensing out of the thermally unstable hot gas. The 230 GHz luminosity of the central continuum source is 500 times greater than its low frequency radio luminosity and probably reflects a recent accretion event by the central supermassive black hole. The spectrum of the central continuum source also exhibits an absorption feature.
    The Astrophysical Journal 07/2014; 792(2). DOI:10.1088/0004-637X/792/2/94
  • Conference Paper: SOFIA Pointing History
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    ABSTRACT: The original pointing accuracy requirement of the Stratospheric Observatory for Infrared Astronomy SOFIA was defined at the beginning of the program in the late 1980s as very challenging 0.2 arcsec rms. The early science flights of the observatory started in December 2010 and the observatory has reached in the mean time nearly 0.7 arcsec rms, which is sufficient for most of the SOFIA science instruments. NASA and DLR, the owners of SOFIA, are planning now a future 4 year program to bring the pointing down to the ultimate 0.2 arcsec rms. This may be the right time to recall the history of the pointing requirement and its verification and the possibility of its achievement via early computer models and wind tunnel tests, later computer aided end-to-end simulations up to the first commissioning flights some years ago. The paper recollects the tools used in the different project phases for the verification of the pointing performance, explains the achievements and may give hints for the planning of the upcoming final pointing improvement phase.
    SPIE 9145, Ground-based and Airborne Telescopes V, Montreal, Canada; 06/2014
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    ABSTRACT: The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities are viewed as a first comprehensive assessment of the Observatory's performance and are used to guide future development activities, as well as to identify additional Observatory upgrades. Pointing stability was evaluated, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an active mass damper system installed on the telescope. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have also been performed. Additional tests targeted basic Observatory capabilities and requirements, including pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights and presents current SOFIA Observatory performance and characterization.
    The Astrophysical Journal Supplement Series 05/2014; 212(2). DOI:10.1088/0067-0049/212/2/24
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    ABSTRACT: It is commonly thought that AGN feedback can break the self-similar scaling relations of galaxies, groups, and clusters. Using high-resolution 3D hydrodynamic simulations, we isolate the impact of AGN feedback on the $L_{\rm x}-T_{\rm x} $ relation, testing the two archetypal and common regimes, self-regulated mechanical feedback and a quasar thermal blast. We find that AGN feedback has severe difficulty in breaking the relation in a consistent way. The similarity breaking is directly linked to the gas evacuation within $R_{500}$, while the central cooling times are inversely proportional to the core density. Breaking self-similarity implies thus breaking the cool core, morphing all systems to non-cool-core objects, which is in clear contradiction with the observed data populated by several cool-core systems. Self-regulated feedback, which quenches cooling flows and preserves cool cores, prevents the dramatic evacuation and similarity breaking at any scale; the relation scatter is also limited. The impulsive thermal blast can break the core-included $L_{\rm x}-T_{\rm x}$ at $T_{500} < 1$ keV, but substantially empties and overheats the halo, generating a perennial non-cool-core group, as experienced by cosmological simulations. Even with partial evacuation, massive systems remain overheated. We show the action of purely AGN feedback is to lower the luminosity and heating the gas, perpendicular to the fit.
    The Astrophysical Journal Letters 01/2014; 783(1). DOI:10.1088/2041-8205/783/1/L10
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    ABSTRACT: We report on deep near-infrared observations obtained with the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) of the first five confirmed gravitational lensing events discovered by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We succeed in disentangling the background galaxy from the lens to gain separate photometry of the two components. The HST data allow us to significantly improve on previous constraints of the mass in stars of the lensed galaxy and to perform accurate lens modelling of these systems, as described in the accompanying paper by Dye et al. We fit the spectral energy distributions of the background sources from near-IR to millimetre wavelengths and use the magnification factors estimated by Dye et al. to derive the intrinsic properties of the lensed galaxies. We find these galaxies to have star-formation rates of approximately 400 to 2000 M_sol/yr, with approximately (6-25)x10^10 M_sol of their baryonic mass already turned into stars. At these rates of star formation, all remaining molecular gas will be exhausted in less than 100 Myr, reaching a final mass in stars of a few 10^11 M_sol. These galaxies are thus proto-ellipticals caught during their major episode of star formation, and observed at the peak epoch z=1.5-3 of the cosmic star formation history of the Universe.
    Monthly Notices of the Royal Astronomical Society 11/2013; 440(3). DOI:10.1093/mnras/stu413
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    ABSTRACT: We compute the properties of a sample of 221 local early-type galaxies with a spectral energy distribution (SED) modelling software, CIGALEMC. Concentrating on the star forming activity and dust contents, we derive parameters such as the specific star formation rate, the dust luminosity, dust mass and temperature. 52 % of our sample is composed of elliptical (E) galaxies and 48 % of lenticular (S0) galaxies. We find a larger proportion of S0 galaxies among galaxies with a large specific star formation rate (sSFR) and large specific dust emission. The stronger activity of S0 galaxies is confirmed by larger dust masses. We investigate the relative proportion of active galactic nuclei (AGN) and star-forming (SF) galaxies in our sample using spectroscopic SDSS data and near-infrared selection techniques, and find a larger proportion of AGN dominated galaxy in the S0 sample than the E one. This could corroborate a scenario where blue galaxies evolve into red ellipticals by passing through a S0 AGN active period while quenching its star formation. Finally, we find a good agreement comparing our estimates with color indicators.
    The Astrophysical Journal 09/2013; 783(2). DOI:10.1088/0004-637X/783/2/135
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    ABSTRACT: The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 5-40 μm imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60-240 μm, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.3-1.1 μm imager, developed at Lowell Observatory. FLITECAM is a 1-5 μm wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42-210 μm integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 5-28 μm high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50-240 μm imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2013; DOI:10.1117/12.2022791
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    ABSTRACT: The Hubble morphological sequence from early to late galaxies corresponds to an increasing rate of specific star formation. The Hubble sequence also follows a banana-shaped correlation between 24 and 70 μm luminosities, both normalized with the K-band luminosity. We show that this correlation is significantly tightened if galaxies with central active galactic nucleus (AGN) emission are removed, but the cosmic scatter of elliptical galaxies in both 24 and 70 μm luminosities remains significant along the correlation. We find that the 24 μm variation among ellipticals correlates with stellar metallicity, reflecting emission from hot dust in winds from asymptotic giant branch stars of varying metallicity. Infrared surface brightness variations in elliptical galaxies indicate that the K – 24 color profile is U-shaped for reasons that are unclear. In some elliptical galaxies, cold interstellar dust emitting at 70 and 160 μm may arise from recent gas-rich mergers. However, we argue that most of the large range of 70 μm luminosity in elliptical galaxies is due to dust transported from galactic cores by feedback events in (currently IR-quiet) AGNs. Cooler dusty gas naturally accumulates in the cores of elliptical galaxies due to dust-cooled local stellar mass loss and may accrete onto the central black hole, releasing energy. AGN-heated gas can transport dust in cores 5-10 kpc out into the hot gas atmospheres where it radiates extended 70 μm emission but is eventually destroyed by sputtering. This, and some modest star formation, defines a cycle of dust creation and destruction. Elliptical galaxies evidently undergo large transient excursions in the banana plot in times comparable to the sputtering time or AGN duty cycle, 10 Myr. Normally regarded as passive, elliptical galaxies are the most active galaxies in the IR color-color correlation.
    The Astrophysical Journal 04/2013; 768(1):28. DOI:10.1088/0004-637X/768/1/28
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    ABSTRACT: We present two large, nearby (0.013$\le$z$\le$0.06) samples of Early-Type Galaxies (ETGs): a visually classified sample of 220 ETGs, created using source-matched data from the Galaxy and Mass Assembly (GAMA) database with FIR/sub-mm detections from $Herschel$-ATLAS; and a visually classified sample of 551 ETGs which are undetected with $Herschel$-ATLAS. Active galactic nuclei (AGN) are removed from our samples using optical emission line diagnostics. These samples are scrutinised to determine characteristics of sub-mm detected versus undetected ETGs. We find similarities in the stellar mass distributions of the two ETG samples but testing other properties uncovers significant differences. The sub-mm detected sample is shown to have lower concentration and S\'ersic indices than those in the undetected sample - a result which may be linked to the presence of dust in the former. Optical and UV-optical colours are also shown to be much bluer, indicating that the dust is linked with recent star formation. The intrinsic effective radii are on average 1.5 times larger for the sub-mm detected ETGs. Surface densities and groups data from the GAMA database are examined for the two samples, leading to the conclusion that dusty ETGs inhabit sparser environments than non-dusty ETGs in the nearby universe, although environments of the brightest ETGs are shown to differ the least. Modified Planck functions are fit to the H-ATLAS detected PACS and SPIRE fluxes for ETGs with sub-mm flux densities of at least 3$\sigma$ in the 350$\mu$m SPIRE band, giving a resultant mean cold dust temperature of T$_{d}$=22.1K, with a range of 9-30K. The corresponding mean dust mass is 1.8$\times10^{7}$M$_{\odot}$, with a range of (0.08-35.0)$\times10^{7}$M$_{\odot}$. The dust masses calculated from these fits, normalised by stellar mass, are shown to increase with decreasing stellar mass and bluer colours.
    Monthly Notices of the Royal Astronomical Society 02/2013; 431(2). DOI:10.1093/mnras/stt310
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    ABSTRACT: Using IRAM PdBI we report the detection of H2O in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel H-ATLAS survey. The sources are detected either in the 2_{02}-1_{11} or 2_{11}-2_{02} H_2O emission lines with integrated line fluxes ranging from 1.8 to 14 Jy.km/s. The corresponding apparent luminosities are mu x L_H2O ~ 3-12 x 10^8 Lo, where mu is the lensing magnification factor (3 < mu < 12). These results confirm that H2O lines are among the strongest molecular lines in such galaxies, with intensities almost comparable to those of the high-J CO lines, and same profiles and line widths (200-900 km/s) as the latter. With the current sensitivity of PdBI, H2O can therefore easily be detected in high-z lensed galaxies (with F(500um) > 100 mJy) discovered in the Herschel surveys. Correcting the luminosities for lensing amplification, L_H2O is found to have a strong dependence on the IR luminosity, varying as ~L_IR^{1.2}. This relation which needs to be confirmed with better statistics, may indicate a role of radiative (IR) excitation of the H2O lines, and implies that high-z galaxies with L_IR >~ 10^13 Lo tend to be very strong emitters in H2O, that have no equivalent in the local universe.
    Astronomy and Astrophysics 01/2013; 551(A115). DOI:10.1051/0004-6361/201220811
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    ABSTRACT: We discuss the evolutionary state of five gas-rich early-type galaxies (ETGs) whose integrated properties suggest that these systems are mid-to-late stage minor mergers, extending beyond the Toomre sequence. A variety of multiwavelength data are utilized to explore diagnostics of the merger process, including imaging photometry derived from observations with GALEX, SDSS, WISE and Spitzer. In particular, we interpret mid-infrared spectra (5-14 microns) obtained with the Infrared Spectrograph on Spitzer. Unusual for ETGs, we find strong emission from polycyclic aromatic hydrocarbons bands and singly-ionized atomic lines, likely caused by low-level star formation in these systems. The overall strength of the PAH emission appears correlated with morphologically signatures of the time since the merger/accretion event. We present feature strengths and ratios derived from the mid-infrared spectra together with star formation rate estimates using GALEX FUV and Spitzer 24 micron continuum data to intrepret the stellar content and history for this sample.
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    ABSTRACT: We have measured the clustering properties of low-redshift (z < 0.3) sub-mm galaxies detected at 250 micron in the Herschel-ATLAS Science Demonstration Phase (SDP) field. We selected a sample for which we have high-quality spectroscopic redshifts, obtained from reliably matching the 250-micron sources to a complete (for r < 19.4) sample of galaxies from the GAMA database. Both the angular and spatial clustering strength are measured for all z < 0.3 sources as well as for five redshift slices with thickness delta z=0.05 in the range 0.05 < z < 0.3. Our measured spatial clustering length r_0 is comparable to that of optically-selected, moderately star-forming (blue) galaxies: we find values around 5 Mpc. One of the redshift bins contains an interesting structure, at z = 0.164.
    Monthly Notices of the Royal Astronomical Society 09/2012; 426(4). DOI:10.1111/j.1365-2966.2012.21949.x
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    ABSTRACT: The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities have been viewed as a first comprehensive assessment of the Observatory's performance and will be used to address the development activity that is planned for 2012, as well as to identify additional Observatory upgrades. A series of 8 SOFIA Characterization And Integration flights have been conducted from June to December 2011. The HIPO science instrument in conjunction with the DSI Super Fast Diagnostic Camera (SFDC) have been used to evaluate pointing stability, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an Active Mass Damper system installed on Telescope Assembly. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have been performed using the HIPO+FLITECAM Science Instrument conguration (FLIPO). A number of additional tests and measurements have targeted basic Observatory capabilities and requirements including, but not limited to, pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights and presents current SOFIA Observatory performance and characterization.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2012; DOI:10.1117/12.925736
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    ABSTRACT: We present a pan-chromatic analysis of an unprecedented sample of 1402 250 micron-selected galaxies at z < 0.5 (mean z = 0.24) from the Herschel-ATLAS survey. We complement our Herschel 100-500 micron data with UV-K-band photometry from the Galaxy And Mass Assembly (GAMA) survey and apply the MAGPHYS energy-balance technique to produce pan-chromatic SEDs for a representative sample of 250 micron selected galaxies spanning the most recent 5 Gyr of cosmic history. We derive estimates of physical parameters, including star formation rates, stellar masses, dust masses and infrared luminosities. The typical H-ATLAS galaxy at z < 0.5 has a far-infrared luminosity in the range 10^10 - 10^12 Lsolar (SFR: 1-50 Msolar/yr) thus is broadly representative of normal star forming galaxies over this redshift range. We show that 250 micron-selected galaxies contain a larger mass of dust at a given infra-red luminosity or star formation rate than previous samples selected at 60 micron from IRAS. We derive typical SEDs for H-ATLAS galaxies, and show that the emergent SED shape is most sensitive to specific star formation rate. The optical-UV SEDs also become more reddened due to dust at higher redshifts. Our template SEDs are significantly cooler than existing infra-red templates. They may therefore be most appropriate for inferring total IR luminosities from moderate redshift submillimetre selected samples and for inclusion in models of the lower redshift submillimetre galaxy populations.
    Monthly Notices of the Royal Astronomical Society 08/2012; 427(1). DOI:10.1111/j.1365-2966.2012.21930.x

Publication Stats

1k Citations
440.64 Total Impact Points

Institutions

  • 2008–2014
    • NASA
      Вашингтон, West Virginia, United States
  • 2012
    • University of the Western Cape
      • Department of Physics
      Kaapstad, Western Cape, South Africa
    • University of British Columbia - Vancouver
      • Department of Physics and Astronomy
      Vancouver, British Columbia, Canada
  • 2011–2012
    • University of Canterbury
      • Department of Physics and Astronomy
      Christchurch, Canterbury Region, New Zealand
    • University of Nottingham
      • School of Physics and Astronomy
      Nottigham, England, United Kingdom
  • 2010
    • Cardiff University
      • School of Physics and Astronomy
      Cardiff, Wales, United Kingdom
    • Universität Heidelberg
      Heidelburg, Baden-Württemberg, Germany
  • 2003–2008
    • SETI Institute
      Mountain View, California, United States
  • 1997
    • University of California Observatories
      Santa Cruz, California, United States
  • 1993–1995
    • University of California, Santa Cruz
      Santa Cruz, California, United States