M. A. Malkan

California State University, Los Angeles, Los Ángeles, California, United States

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Publications (302)819.55 Total impact

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    ABSTRACT: The morphology of the circumnuclear gas accreting onto supermassive black holes in Seyfert galaxies remains a topic of much debate. As the innermost regions of Active Galactic Nuclei (AGN) are spatially unresolved, X-ray spectroscopy, and in particular line-of-sight absorption variability, is a key diagnostic to map out the distribution of gas. Observations of variable X-ray absorption in multiple Seyferts and over a wide range of timescales indicate the presence of clumps/clouds of gas within the circumnuclear material. Eclipse events by clumps transiting the line of sight allow us to explore the properties of the clumps over a wide range of radial distances from the optical/UV Broad Line Region (BLR) to beyond the dust sublimation radius. Time-resolved absorption events have been extremely rare so far, but suggest a range of density profiles across Seyferts. We resolve a weeks-long absorption event in the Seyfert NGC 3227. We examine six Suzaku and twelve Swift observations from a 2008 campaign spanning 5 weeks. We use a model accounting for the complex spectral interplay of three differently-ionized absorbers. We perform time-resolved spectroscopy to discern the absorption variability behavior. We also examine the IR-to-X-ray spectral energy distribution (SED) to test for reddening by dust. The 2008 absorption event is due to moderately-ionized ($\log \xi\sim 1.2-1.4$) gas covering 90% of the line of sight. We resolve the density profile to be highly irregular, in contrast to a previous symmetric and centrally-peaked event mapped with RXTE in the same object. The UV data do not show significant reddening, suggesting that the cloud is dust-free. The 2008 campaign has revealed a transit by a filamentary, moderately-ionized cloud of variable density that is likely located in the BLR, and possibly part of a disk wind.
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    ABSTRACT: Multiwavelength Spectral Energy Distributions (SEDs) of far-infrared (FIR) galaxies detected in the AKARI South Ecliptic Poles Survey (ADF-S) allow to trace differences between [Ultra]-Luminous Infrared Galaxies ([U]LIRGS) and other types of star-forming galaxies (SF).
    Proceedings of the International Astronomical Union 07/2015; 10(S309):325. DOI:10.1017/S1743921314010205
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    ABSTRACT: Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure Baryonic Acoustic Oscillations (BAOs) in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the WFC3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of Halpha (Ha) emitters observable by these future surveys. WISP is an ongoing HST slitless spectroscopic survey, covering the 0.8-1.65micron wavelength range and allowing the detection of Ha emitters up to z~1.5 and [OIII] emitters to z~2.3. We derive the Ha-[OIII] bivariate line luminosity function for WISP galaxies at z~1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurement, and demonstrate how it can be used to derive the Ha luminosity function from exclusively fitting [OIII] data. Using the z~2 [OIII] line luminosity function, and assuming that the relation between Ha and [OIII] luminosity does not change significantly over the redshift range, we predict the Ha number counts at z~2 - the upper end of the redshift range of interest for the future surveys. For the redshift range 0.7<z<2, we expect ~3000 galaxies/deg^2 for a flux limit of 3x10^{-16} ergs/s/cm^2 (the proposed depth of Euclid galaxy redshift survey) and ~20,000 galaxies/deg^2 for a flux limit of ~10^{-16} ergs/s/cm^2 (the baseline depth of WFIRST galaxy redshift survey).
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    ABSTRACT: The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essentially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT's science agenda fills all of space and time, from nearby comets and asteroids, to exoplanets, to the most distant galaxies, and all the way back to the very first sources of light in the Universe. More than 150 astronomers from within the TMT partnership and beyond offered input in compiling the new 2015 Detailed Science Case. The contributing astronomers represent the entire TMT partnership, including the California Institute of Technology (Caltech), the Indian Institute of Astrophysics (IIA), the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), the National Astronomical Observatory of Japan (NAOJ), the University of California, the Association of Canadian Universities for Research in Astronomy (ACURA) and US associate partner, the Association of Universities for Research in Astronomy (AURA).
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    ABSTRACT: (Abridged) We aim to study the evolution of dust attenuation in galaxies selected in the IR in the redshift range in which they are known to dominate the star formation activity in the universe. The comparison with other measurements of dust attenuation in samples selected using different criteria will give us a global picture of the attenuation at work in star-forming galaxies and its evolution with redshift. Using multiple filters of IRC instrument, we selected more than 4000 galaxies from their rest-frame emission at 8 microns, from z~0.2 to 2$. We built SEDs from the rest-frame UV to the far-IR by adding data in the optical-NIR and from GALEX and Herschel surveys. We fit SEDs with the physically-motivated code CIGALE. We test different templates for AGNs and recipes for dust attenuation and estimate stellar masses, SFRs, amount of dust attenuation, and AGN contribution to the total IR luminosity. The AGN contribution to the total IR luminosity is found to be on average approximately 10% with a slight increase with redshift. Dust attenuation in galaxies dominating the IR luminosity function is found to increase from z=0 to z=1 and to remain almost constant from z=1 to z=1.5. Conversely, when galaxies are selected at a fixed IR luminosity, their dust attenuation slightly decreases as redshift increases but with a large dispersion. The attenuation in our mid-IR selected sample is found ~ 2 mag higher than that found globally in the universe or in UV and Halpha line selections in the same redshift range. This difference is well explained by an increase of dust attenuation with the stellar mass, in global agreement with other recent studies. Starbursting galaxies do not systematically exhibit a high attenuation
    Astronomy and Astrophysics 04/2015; 577. DOI:10.1051/0004-6361/201425399 · 4.48 Impact Factor
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    ABSTRACT: We present spatially resolved gas-phase metallicity for a system of three galaxies at z=1.85 detected in the Grism Lens-Amplified Survey from Space (GLASS). The combination of HST's diffraction limit and strong gravitational lensing by the cluster MACS J0717+3745 results in a spatial resolution of ~200-300 pc, enabling good spatial sampling despite the intrinsically small galaxy sizes. The galaxies in this system are separated by 50-200 kpc in projection and are likely in an early stage of interaction, evidenced by relatively high specific star formation rates. Their gas-phase metallicities are consistent with larger samples at similar redshift, star formation rate, and stellar mass. We obtain a precise measurement of the metallicity gradient for one galaxy and find a shallow slope compared to isolated galaxies at high redshift, consistent with a flattening of the gradient due to gravitational interaction. An alternative explanation for the shallow metallicity gradient and elevated star formation rate is rapid recycling of metal-enriched gas, but we find no evidence for enhanced gas-phase metallicities which should result from this effect. Notably, the measured stellar masses log(M/Msun) = 7.2-9.1 probe to an order of magnitude below previous mass-metallicity studies at this redshift. The lowest mass galaxy has properties similar to those expected for Fornax at this redshift, indicating that GLASS is able to directly study the progenitors of local group dwarf galaxies on spatially resolved scales. Larger samples from the full GLASS survey will be ideal for studying the effects of feedback, and the time evolution of metallicity gradients. These initial results demonstrate the utility of HST spectroscopy combined with gravitational lensing for characterizing resolved physical properties of galaxies at high redshift.
    The Astronomical Journal 03/2015; 149(3):107. DOI:10.1088/0004-6256/149/3/107 · 4.05 Impact Factor
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    ABSTRACT: We present [CII] observations of 20 strongly lensed dusty star forming galaxies at 2.1 < z < 5.7 using APEX and Herschel. The sources were selected on their 1.4 mm flux (S_1.4mm > 20 mJy) from the South Pole Telescope survey, with far-infrared (FIR) luminosities determined from extensive photometric data. The [CII] line is robustly detected in 17 sources, all but one being spectrally resolved. Eleven out of 20 sources observed in [CII] also have low-J CO detections from ATCA. A comparison with mid- and high-J CO lines from ALMA reveals consistent [CII] and CO velocity profiles, suggesting that there is little differential lensing between these species. The [CII], low-J CO and FIR data allow us to constrain the properties of the interstellar medium. We find [CII] to CO(1-0) luminosity ratios in the SPT sample of 5200 +- 1800, with significantly less scatter than in other samples. This line ratio can be best described by a medium of [CII] and CO emitting gas with a higher [CII] than CO excitation temperature, high CO optical depth tau_CO >> 1, and low to moderate [CII] optical depth tau_CII ~< 1. The geometric structure of photodissociation regions allows for such conditions.
    Monthly Notices of the Royal Astronomical Society 01/2015; 449(3). DOI:10.1093/mnras/stv372 · 5.23 Impact Factor
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    ABSTRACT: We present data products from the 300 ks Chandra survey in the AKARI North Ecliptic Pole Deep Field. This field has a unique set of nine-band infrared photometry covering 2–24 μm from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ∼15 μm, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z ∼ 1. We design a source detection procedure, which performs joint maximum likelihood PSF (point spread function) fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 deg2. The procedure has been highly optimized and tested by simulations. We provide a point source catalogue with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5–7, 0.5–2, 2–7, 2–4, and 4–7 keV bands. The catalogue contains 457 X-ray sources and the spurious fraction is estimated to be ∼1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical–MIR counterparts in the central 0.25 deg2, where deep Subaru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ∼80 per cent have optical counterparts and ∼60 per cent also have AKARI MIR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. Around 30 per cent of all AGN that have MIR SEDs purely explainable by AGN activity are strong Compton-thick AGN candidates.
    Monthly Notices of the Royal Astronomical Society 09/2014; 446(1). DOI:10.1093/mnras/stu2010 · 5.23 Impact Factor
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    ABSTRACT: We analyze the two-dimensional distribution and kinematics of the stars as well as molecular and ionized gas in the central few hundred parsecs of five active and five matched inactive galaxies. The equivalent widths of the Br gamma line indicate that there is no ongoing star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0 S(1) H-2 kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H-2 kinematics reveal inflow and outflow superimposed on disk rotation. Steady-state circumnuclear inflow is seen in three active galactic nuclei (AGNs), and hydrodynamical models indicate it can be driven by a large-scale bar. In three of the five AGNs, molecular outflows are spatially resolved. The outflows are oriented such that they intersect, or have an edge close to, the disk, which may be the source of molecular gas in the outflow. The relatively low speeds imply the gas will fall back onto the disk, and with moderate outflow rates, they will have only a local impact on the host galaxy. H-2 was detected in two inactive galaxies. These exhibit chaotic circumnuclear dust morphologies and have molecular structures that are counter-rotating with respect to the main gas component, which could lead to gas inflow in the near future. In our sample, all four galaxies with chaotic dust morphology in the circumnuclear region exist in moderately dense groups with 10-15 members where accretion of stripped gas can easily occur.
    The Astrophysical Journal 09/2014; 792(2):101. DOI:10.1088/0004-637X/792/2/101 · 6.28 Impact Factor
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    ABSTRACT: We present time series analyses of the full Kepler dataset of Zw 229-15. This Kepler light curve --- with a baseline greater than three years, composed of virtually continuous, evenly sampled 30-minute measurements --- is unprecedented in its quality and precision. We utilize two methods of power spectral analysis to investigate the optical variability and search for evidence of a bend frequency associated with a characteristic optical variability timescale. Each method yields similar results. The first interpolates across data gaps to use the standard Fourier periodogram. The second, using the CARMA-based time-domain modeling technique of Kelly et al. (2014), does not need evenly-sampled data. Both methods find excess power at high frequencies that may be due to Kepler instrumental effects. More importantly both also show strong bends ({\Delta}{\alpha} ~ 2) at timescales of ~5 days, a feature similar to those seen in the X-ray PSDs of AGN but never before in the optical. This observed ~5 day timescale may be associated with one of several physical processes potentially responsible for the variability. A plausible association could be made with light-crossing, dynamical or thermal timescales, depending on the assumed value of the accretion disk size and on unobserved disk parameters such as {\alpha} and H/R. This timescale is not consistent with the viscous timescale, which would be years in a ~10^7 Solar mass AGN such as Zw 229-15. However there must be a second bend on long (>~1 year) timescales, and that feature could be associated with the viscous timescale.
    The Astrophysical Journal 09/2014; 795(1). DOI:10.1088/0004-637X/795/1/2 · 6.28 Impact Factor
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    ABSTRACT: We analyse the 2-dimensional distribution and kinematics of the stars as well as molecular and ionised gas in the central few hundred parsecs of 5 active and 5 matched inactive galaxies. The equivalent widths of the Br-gamma line indicate there is no on-going star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0S(1) H_2 kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H_2 kinematics reveal inflow and outflow superimposed on disk rotation. Steady-state circumnuclear inflow is seen in three AGN, and hydrodynamical models indicate it can be driven by a large scale bar. In three of the five AGN, molecular outflows are spatially resolved. The outflows are oriented such that they intersect, or have an edge close to, the disk - which may be the source of molecular gas in the outflow. The relatively low speeds imply the gas will fall back onto the disk; and with moderate outflow rates, they will have only a local impact on the host galaxy. H_2 was detected in two inactive galaxies. These exhibit chaotic circumnuclear dust morphologies and have molecular structures that are counter-rotating with respect to the main gas component, which could lead to gas inflow in the near future. In our sample, all four galaxies with chaotic dust morphology in the circumnuclear region exist in moderately dense groups with 10-15 members where accretion of stripped gas can easily occur.
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    ABSTRACT: In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 μm luminosity functions (LFs) at 0.006 ≤z ≤ 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 μm and 25,721 galaxies at 22 μm for spectroscopic classification. We then identified 16,355 AGNs at 12 μm and 4683 AGNs at 22 μm by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z ≤ 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
    The Astrophysical Journal 05/2014; 788(1):45. DOI:10.1088/0004-637X/788/1/45 · 6.28 Impact Factor
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    ABSTRACT: We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250-770GHz. This spectrum was constructed by stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral features of 12CO, [CI], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the 13CO brightness in these objects is comparable to that of the only other z>2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4-1.2mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.
    The Astrophysical Journal 03/2014; 785(2). DOI:10.1088/0004-637X/785/2/149 · 6.28 Impact Factor
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    ABSTRACT: The \emph{Grism Lens-Amplified Survey from Space} (GLASS) is a Hubble Space Telescope (\HST) Large Program, which will obtain 140 orbits of grism spectroscopy of the core and infall regions of 10 galaxy clusters, selected to be among the very best cosmic telescopes. Extensive \HST\ imaging is available from many sources including the CLASH and Frontier Field programs. We introduce the survey by analyzing spectra of faint multiply-imaged galaxies and $z\gtrsim6$ galaxy candidates obtained from the first seven orbits targeting the core of the Frontier Field cluster MACS0717.5+3745. Using the G102 and G141 grisms to cover the wavelength range 0.8--1.7$\mu$m, we confirm 4 strongly lensed systems by detecting emission lines in each of the images. For the 9 $z\gtrsim6$ galaxy candidates clear from contamination, we do not detect any emission line down to a 1-$\sigma$ noise level of $\sim$5$\times$10$^{-18}$\cgs. Taking lensing magnification into account, our flux sensitivity reaches $\sim$0.2--5$\times$10$^{-18}$\cgs. These limits over an uninterrupted wavelength range rule out the possibility that the high-$z$ galaxy candidates are instead strong line emitters at lower redshift. These results show that by means of careful modeling of the background--- and with the assistance of lensing magnification---interesting flux limits can be reached for large numbers of objects, avoiding pre-selection and the wavelength restrictions inherent to ground-based multi-slit spectroscopy. These observations confirm the power of slitless \HST\ spectroscopy even in fields as crowded as a cluster core.
    The Astrophysical Journal Letters 01/2014; DOI:10.1088/2041-8205/782/2/L36 · 5.60 Impact Factor
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    ABSTRACT: We present near-infrared emission line counts and luminosity functions from the HST WFC3 Infrared Spectroscopic Parallels (WISP) program for 29 fields observed using both the G102 and G141 grism. Using these derived emission line counts we make predictions for future space missions, like WFIRST, that will make extensive use of slitless grism spectroscopy in the near-IR over large areas of sky. The WISP survey is sensitive to fainter flux levels (3-5x10^-17 ergs/s/cm2) than the near-infrared grism missions aimed at baryonic acoustic oscillation cosmology (1-4x10^-16 ergs/s/cm2), allowing us to both investigate the fainter emission lines the large area surveys will be missing and make count predictions for the deeper grism pointings that are likely to be done over smaller areas. Cumulative number counts of 0.7<z<1.5 galaxies reach 10,000 square degrees above an H-alpha flux of 2x10^{-16} ergs/s/cm2. Galaxies with low H-alpha/[OIII] ratios are very rare at the brighter fluxes that future near-infrared grism surveys will probe; our survey finds no galaxies with H-alpha/[OIII < 0.95 that have H-alpha flux greater than 3x10^-16 ergs/s/cm2. We find good agreement between our derived luminosity functions and those from narrow band H-alpha surveys, like those of HiZELS (Sobral et al. 2013) and New Halpha (Ly et. 2011). The evolution in both the H-alpha luminosity function from z=0.3-1.5 and the [OIII] luminosity function from z=0.7-2.3 is almost entirely in the L* parameter, which steadily increases with redshift over those ranges. We will also present simulations of future large area near-infrared grism spectroscopy, based on the observed distributions of emission line fluxes, galaxy sizes, redshifts, H-alpha/[OIII] ratios, and equivalent widths seen in the WISP survey.
  • Jong-Hak Woo · D. Park · V. Bennert · T. Treu · M. A. Malkan · M. Auger
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    ABSTRACT: The scaling relations between black hole mass and galaxy global properties indicate a close connection between black hole growth and galaxy evolution. Based on the M-sigma relation of the most updated reverberation-mapped AGNs, we determine the virial factor for AGN black hole mass recipes, and applied it to a sample of 42 moderate-luminosity AGNs at 0.4 and 0.6. The sample has been observed with the HST (ACS, NICMOS, and WFC3) and the Keck telescope in order to measure bulge luminosity and stellar velocity dispersion of their host galaxies. By investigating cosmic evolution of the M-bulge luminosity and M-sigma relations over the last 6 Gyr, we find that black holes in the past lived in a smaller or lower luminosity bulges compared to the present-day black holes, as consistent with various previous works. The uncertainty of the single-epoch black hole mass is still a dominant hindrance in unveiling the nature of the black hole-galaxy connection, particularly at high redshift.
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    ABSTRACT: Near-infrared reverberation measurements have proven to be a valuable tool for mapping the location of hot dust in active galactic nuclei (AGNs). Ground-based campaigns have shown that the K-band continuum varies in response to changes in the optical continuum, and measurements of the K-band lag time give the size scale of the hot dust emission region, which likely corresponds to the dust sublimation radius. Reverberation measurements at longer wavelengths can add valuable information on the dust temperature profile in AGNs and the structure of the putative dusty torus. We have conducted a space based monitoring campaign of the Seyfert 1 galaxy Zw 229-015 using optical data from the Kepler Space Telescope and infrared data (3.6 micron) from the Spitzer Space telescope. We have also augmented the optical data with multiple ground based observatories. We have detected infrared reverberation both on short and long timescales.
  • Bryan Scott · V. Bennert · S. Komossa · T. Treu · M. Auger · M. A. Malkan
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    ABSTRACT: High-quality Keck/LRIS long-slit spectra for a sample of 97 Type 1 local active galaxies selected from the Sloan Digital Sky Survey (0.02 ≦ z ≦ 0.1; MBH ≦107 M⊙) are used to study the relations between black hole mass (MBH) and host-galaxy properties. Of these objects, eight were found to be lacking broad Hβ emission lines previously observed in SDSS spectra. Based on seeing and PSF profile, we can exclude the lack of broad lines in the Keck spectra as being due to a telescope pointing error, missing the central AGN. These AGNs are classified as type 1 or type 1.5 Seyferts according to the characteristic presence of broad lines in SDSS spectra, and as 1.8 or 1.9 Seyferts in Keck spectra. We discuss various explanations for this transition including time variation of the torus, time variation of the broad line region, and galaxy mergers resulting in an AGN off-center from the host-galaxy nucleus (including the possibility of a gravitational recoil). Follow up observations at Lick Observatory are used to constrain the different scenarios.
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    ABSTRACT: We present observations of SPT-S J053816–5030.8, a gravitationally lensed dusty star-forming galaxy (DSFG) at z = 2.7817 that was first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538–50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538–50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, the Very Large Telescope, ATCA, APEX, and the Submillimeter Array. We use high-resolution imaging from the Hubble Space Telescope to de-blend SPT 0538–50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 ± 4), we derive the intrinsic properties of SPT 0538–50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and—using molecular line fluxes—the excitation conditions within the interstellar medium. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538–50 similar to local starburst galaxies and unlike that seen in some other DSFGs at this epoch.
    The Astrophysical Journal 12/2013; 779(1):67. DOI:10.1088/0004-637X/779/1/67 · 6.28 Impact Factor
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    ABSTRACT: The main aim of this work is the characterization of physical properties of galaxies detected in the far infrared (FIR) in the AKARI Deep Field-South (ADF-S) survey. Starting from a catalog of the 1 000 brightest ADF-S sources in the WIDE-S (90$\mu$m) AKARI band, we constructed a subsample of galaxies with spectral coverage from the ultraviolet to the far infrared. We then analyzed the multiwavelength properties of this 90$\mu$m selected sample of galaxies. For galaxies without known spectroscopic redshifts we computed photometric redshifts using the codes Photometric Analysis for Redshift Estimate (Le PHARE) and Code Investigating GALaxy Emission (CIGALE), tested these photometric redshifts using spectroscopic redshifts, and compared the performances of both codes. To test the reliability of parameters obtained by fitting spectral energy distributions, a mock cataloge was generated. We built a large multiwavelength catalog of more than 500 ADF-S galaxies. We successfully fitted Spectral Energy Distributions of 186 galaxies with $\rm{\chi^2_{min}<4}$, and analyzed the output parameters of the fits. We conclude that our sample consists mostly of nearby actively star-forming galaxies, and all our galaxies have a relatively high metallicity. We estimated photometric redshifts for 113 galaxies from the whole ADF-S sample. Comparing the performance of Le PHARE and CIGALE, we found that CIGALE gives more reliable redshift estimates for our galaxies, which implies that including the IR photometry allows for substantial improvement of photometric redshift estimation.
    Astronomy and Astrophysics 12/2013; 562. DOI:10.1051/0004-6361/201321665 · 4.48 Impact Factor

Publication Stats

6k Citations
819.55 Total Impact Points

Institutions

  • 2014
    • California State University, Los Angeles
      • Department of Physics and Astronomy
      Los Ángeles, California, United States
    • Nagoya University
      • Graduate School of Science
      Nagoya, Aichi, Japan
  • 1988–2014
    • University of California, Los Angeles
      • • Department of Physics and Astronomy
      • • Division of Astronomy & Astrophysics
      Los Ángeles, California, United States
  • 2013
    • University of Colorado at Boulder
      • Department of Astrophysical and Planetary Sciences
      Boulder, Colorado, United States
  • 2012
    • McGill University
      • Department of Physics
      Montréal, Quebec, Canada
  • 2005
    • National Astronomical Observatory of Japan
      • Division of Optical and Infrared Astronomy
      Edo, Tōkyō, Japan
  • 2004
    • Tel Aviv University
      • Department of Physics and Astronomy
      Tell Afif, Tel Aviv, Israel
  • 1999
    • Cornell University
      • Department of Astronomy
      Ithaca, New York, United States
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
  • 1998–1999
    • Wellesley College
      • Department of Astronomy
      Уэлсли, Massachusetts, United States
  • 1996
    • University of Birmingham
      • School of Physics and Astronomy
      Birmingham, England, United Kingdom
  • 1994
    • Johns Hopkins University
      • Department of Physics and Astronomy
      Baltimore, Maryland, United States
  • 1984
    • University of Washington Seattle
      Seattle, Washington, United States
  • 1982
    • California Institute of Technology
      • Jet Propulsion Laboratory
      Pasadena, California, United States