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Search Results: 1 - 10 of 15 matches for " Wiphu Rujopakarn "
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Morphology and Size Differences between Local & High Redshift Luminous Infrared Galaxies
Wiphu Rujopakarn,George H. Rieke,Daniel J. Eisenstein,Stephanie Juneau
Physics , 2010, DOI: 10.1088/0004-637X/726/2/93
Abstract: We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z ~ 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z ~ 1 and a lensed galaxy at z ~ 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z > 1 for a given IR luminosity compared to their local counterparts.
Variability of the Infrared Excess of Extreme Debris Disks
Huan Y. A. Meng,George H. Rieke,Kate Y. L. Su,Valentin D. Ivanov,Leonardo Vanzi,Wiphu Rujopakarn
Physics , 2012, DOI: 10.1088/2041-8205/751/1/L17
Abstract: Debris disks with extremely large infrared excesses (fractional luminosities $> 10^{-2}$) are rare. Those with ages between 30 and 130 Myr are of interest because their evolution has progressed well beyond that of protoplanetary disks (which dissipate with a timescale of order 3 Myr), yet they represent a period when dynamical models suggest that terrestrial planet building may still be progressing through large, violent collisions that could yield large amounts of debris and large infrared excesses. For example, our Moon was formed through a violent collision of two large proto-planets during this age range. We report two disks around the solar-like stars ID8 and HD 23514 in this age range where the 24 {\mu}m infrared excesses vary on timescales of a few years, even though the stars are not variable in the optical. Variations this rapid are difficult to understand if the debris is produced by collisional cascades, as it is for most debris disks. It is possible that the debris in these two systems arises in part from condensates from silicate-rich vapor produced in a series of violent collisions among relatively large bodies. If their evolution is rapid, the rate of detection of extreme excesses would indicate that major collisions may be relatively common in this age range.
Large Impacts around a Solar Analog Star in the Era of Terrestrial Planet Formation
Huan Y. A. Meng,Kate Y. L. Su,George H. Rieke,David J. Stevenson,Peter Plavchan,Wiphu Rujopakarn,Carey M. Lisse,Saran Poshyachinda,Daniel E. Reichart
Physics , 2015, DOI: 10.1126/science.1255153
Abstract: The final assembly of terrestrial planets occurs via massive collisions, which can launch copious clouds of dust that are warmed by the star and glow in the infrared. We report the real-time detection of a debris-producing impact in the terrestrial planet zone around a 35-million year-old solar analog star. We observed a substantial brightening of the debris disk at 3-5 {\mu}m, followed by a decay over a year, with quasi-periodic modulations of the disk flux. The behavior is consistent with the occurrence of a violent impact that produced vapor out of which a thick cloud of silicate spherules condensed that were ground into dust by collisions. These results demonstrate how the time domain can become a new dimension for the study of terrestrial planet formation.
Planetary Collisions outside the Solar System: Time Domain Characterization of Extreme Debris Disks
Huan Y. A. Meng,Kate Y. L. Su,George H. Rieke,Wiphu Rujopakarn,Gordon Myers,Michael Cook,Emery Erdelyi,Chris Maloney,James McMath,Gerald Persha,Saran Poshyachinda,Daniel E. Reichart
Physics , 2015, DOI: 10.1088/0004-637X/805/1/77
Abstract: Luminous debris disks of warm dust in the terrestrial planet zones around solar-like stars are recently found to vary, indicative of ongoing large-scale collisions of rocky objects. We use Spitzer 3.6 and 4.5 {\mu}m time-series observations in 2012 and 2013 (extended to 2014 in one case) to monitor 5 more debris disks with unusually high fractional luminosities ("extreme debris disk"), including P1121 in the open cluster M47 (80 Myr), HD 15407A in the AB Dor moving group (80 Myr), HD 23514 in the Pleiades (120 Myr), HD 145263 in the Upper Sco Association (10 Myr), and the field star BD+20 307 (>1 Gyr). Together with the published results for ID8 in NGC 2547 (35 Myr), this makes the first systematic time-domain investigation of planetary impacts outside the solar system. Significant variations with timescales shorter than a year are detected in five out of the six extreme debris disks we have monitored. However, different systems show diverse sets of characteristics in the time domain, including long-term decay or growth, disk temperature variations, and possible periodicity.
The Evolution of the Star Formation Rate of Galaxies at 0.0 < z < 1.2
Wiphu Rujopakarn,Daniel J. Eisenstein,George H. Rieke,Casey Papovich,Richard J. Cool,John Moustakas,Buell T. Januzzi,Christopher S. Kochanek,Marcia J. Rieke,Arjun Dey,Peter Eisenhardt,Steve S. Murray,Michael J. I. Brown,Emeric Le Floc'h
Physics , 2010, DOI: 10.1088/0004-637X/718/2/1171
Abstract: We present the 24 micron rest-frame luminosity function (LF) of star-forming galaxies in the redshift range 0.0 < z < 0.6 constructed from 4047 spectroscopic redshifts from the AGN and Galaxy Evolution Survey of 24 micron selected sources in the Bootes field of the NOAO Deep Wide-Field Survey. This sample provides the best available combination of large area (9 deg^2), depth, and statistically complete spectroscopic observations, allowing us to probe the evolution of the 24 micron LF of galaxies at low and intermediate redshifts while minimizing the effects of cosmic variance. In order to use the observed 24 micron luminosity as a tracer for star formation, active galactic nuclei (AGNs) that could contribute significantly at 24 micron are identified and excluded from our star-forming galaxy sample based on their mid-IR spectral energy distributions or the detection of X-ray emission. The evolution of the 24 micron LF of star-forming galaxies for redshifts of z < 0.65 is consistent with a pure luminosity evolution where the characteristic 24 micron luminosity evolves as (1+z)^(3.8+/-0.3). We extend our evolutionary study to encompass 0.0 < z < 1.2 by combining our data with that of the Far-Infrared Deep Extragalactic Legacy Survey. Over this entire redshift range the evolution of the characteristic 24 micron luminosity is described by a slightly shallower power law of (1+z)^(3.4+/-0.2). We find a local star formation rate density of (1.09+/-0.21) x 10^-2 Msun/yr/Mpc^-3, and that it evolves as (1+z)^(3.5+/-0.2) over 0.0 < z < 1.2. These estimates are in good agreement with the rates using optical and UV fluxes corrected for the effects of intrinsic extinction in the observed sources. This agreement confirms that star formation at z <~ 1.2 is robustly traced by 24 micron observations and that it largely occurs in obscured regions of galaxies. (Abridged)
SXDF-ALMA 1.5 arcmin^2 deep survey. A compact dusty star-forming galaxy at z=2.5
Ken-ichi Tadaki,Kotaro Kohno,Tadayuki Kodama,Soh Ikarashi,Itziar Aretxaga,Stefano Berta,Karina I. Caputi,James S. Dunlop,Bunyo Hatsukade,Masao Hayashi,David H. Hughes,Rob Ivison,Takuma Izumi,Yusei Koyama,Dieter Lutz,Ryu Makiya,Yuichi Matsuda,Kouichiro Nakanishi,Wiphu Rujopakarn,Yoichi Tamura,Hideki Umehata,Wei-Hao Wang,Grant W. Wilson,Stijn Wuyts,Yuki Yamaguchi,Min S. Yun
Physics , 2015, DOI: 10.1088/2041-8205/811/1/L3
Abstract: We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1 mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19 or z=2.53. We have detected continuum emission from three of our Halpha-selected sample, including one compact star-forming galaxy with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M*/Msun)>10.9 whereas the other blue, main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290 uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02, to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the concentrated starburst can within less than 50^{+12}_{-11} Myr build up a stellar surface density matching that of massive compact galaxies at z~2, provided at least 19+-3% of the total gas is converted into stars in the galaxy centre. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction (23+-8%) and is located in the lower envelope of the star formation main-sequence. This compact less star-forming galaxy is likely to be in an intermediate phase between compact dusty star-forming and quiescent galaxies.
Mid-Infrared Determination of Total Infrared Luminosity and Star Formation Rates of Local and High-Redshift Galaxies
W. Rujopakarn,G. H. Rieke,B. J. Weiner,P. Pérez-González,M. Rex,G. L. Walth,J. S. Kartaltepe
Physics , 2011, DOI: 10.1088/0004-637X/767/1/73
Abstract: We demonstrate estimating the total infrared luminosity, LIR, and star formation rates (SFRs) of star-forming galaxies at redshift 0 < z < 2.8 from single-band 24 micron observations, using local spectral energy distributions (SED) templates without introducing additional free parameters. Our method is based on characterizing the SEDs of galaxies as a function of their LIR surface density, which is motivated by the indications that the majority of IR luminous star-forming galaxies at 1 < z < 3 have extended star-forming regions, in contrast to the strongly nuclear concentrated, merger-induced starbursts in local luminous and ultraluminous IR galaxies. We validate our procedure for estimating LIR by comparing the resulting LIRs with those measured from far-IR observations at 0 < z < 2.8. AGNs were excluded using X-ray and 3.6-8.0 micron observations, which are generally available in deep cosmological survey fields. The Gaussian fits to the distribution of the discrepancies between the LIR measurements from single-band 24 micron and Herschel observations have sigma < 0.1 dex, with ~10% of objects disagreeing by more than 0.2 dex. Since the 24 micron estimates are based on SEDs for extended galaxies, this agreement suggests that ~90% of IR galaxies at high z are indeed much more physically extended than local counterparts of similar LIR, consistent with recent independent studies of the fractions of galaxies forming stars in the main-sequence and starburst modes, respectively. Because we have not introduced empirical corrections to enhance these estimates, in principle, our method should be applicable to lower luminosity galaxies. This will enable use of the 21 micron band of the Mid-Infrared Instrument (MIRI) on board the JWST to provide an extremely sensitive tracer of obscured SFR in individual star-forming galaxies across the peak of the cosmic star formation history.
LBT and Spitzer Spectroscopy of Star-Forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators
W. Rujopakarn,G. H. Rieke,C. J. Papovich,B. J. Weiner,J. R. Rigby,M. Rex,F. Bian,O. P. Kuhn,D. Thompson
Physics , 2012, DOI: 10.1088/0004-637X/755/2/168
Abstract: We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample was selected to represent pure, actively star-forming systems, absent of active galactic nuclei. The large lensing magnifications result in high signal-to-noise spectra that can probe faint IR recombination lines, including Pa-alpha and Br-alpha at high redshifts. The sample was augmented by three lensed galaxies with similar suites of unpublished data and observations from the literature, resulting in the final sample of seven galaxies. We use the IR recombination lines in conjunction with H-alpha observations to probe the extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from ~0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z ~ 2 must take careful count of extinction in the most IR luminous galaxies. We also measure extinction by comparing SFR estimates from optical emission lines with those from far-IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 < z < 3. Without correcting for dust extinction, the H-alpha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2 micron PAH emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, ~0.2 dex scatter is observed.
Looking Into the Fireball: ROTSE-III and Swift Observations of Early GRB Afterglows
E. S. Rykoff,F. Aharonian,C. W. Akerlof,M. C. B. Ashley,S. D. Barthelmy,H. A. Flewelling,N. Gehrels,E. Gogus,T. Guver,U. Kiziloglu,H. A. Krimm,T. A. McKay,M. Ozel,A. Phillips,R. M. Quimby,G. Rowell,W. Rujopakarn,B. E. Schaefer,D. A. Smith,W. T. Vestrand,J. C. Wheeler,J. Wren,F. Yuan,S. A. Yost
Physics , 2009, DOI: 10.1088/0004-637X/702/1/489
Abstract: We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the ROTSE-III telescope network from March 2005 through June 2007. This set is comprised of 12 afterglows with early optical and Swift/XRT observations, with a median ROTSE-III response time of 45 s after the start of gamma-ray emission (8 s after the GCN notice time). These afterglows span four orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100
Monster in the Dark: The Ultraluminous GRB 080607 and its Dusty Environment
Daniel A. Perley,A. N. Morgan,A. Updike,F. Yuan,C. W. Akerlof,A. A. Miller,J. S. Bloom,S. B. Cenko,W. Li,A. V. Filippenko,J. X. Prochaska,D. A. Kann,N. R. Butler,P. Christian,D. H. Hartmann,P. Milne,E. S. Rykoff,W. Rujopakarn,J. C. Wheeler,G. G. Williams
Physics , 2010, DOI: 10.1088/0004-6256/141/2/36
Abstract: We present early-time optical through infrared photometry of the bright gamma-ray burst GRB 080607, starting only 6 s following the initial trigger in the rest frame. Complemented by our previously published spectroscopy, this high-quality photometric dataset allows us to solve for the extinction properties of the redshift 3.036 sightline, giving perhaps the most detailed information on the ultraviolet continuum absorption properties of any sightline outside our Local Group to date. The extinction properties are not adequately modeled by any ordinary extinction template (including the average Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud curves), partially because the 2175-Angstrom feature (while present) is weaker by about a factor of two than when seen under similar circumstances locally. However, the spectral energy distribution is exquisitely fitted by the more general Fitzpatrick & Massa (1990) parameterization of Local-Group extinction, putting it in the same family as some peculiar Milky Way extinction curves. After correcting for this (considerable, A_V = 3.3 +/- 0.4 mag) extinction, GRB 080607 is revealed to have been among the most optically luminous events ever observed, comparable to the naked-eye burst GRB 080319B. Its early peak time (t_rest < 6 s) indicates a high initial Lorentz factor (Gamma > 600), while the extreme luminosity may be explained in part by a large circumburst density. Only because of its early high luminosity could the afterglow of GRB 080607 be studied in such detail in spite of the large attenuation and great distance, making this burst an excellent prototype for the understanding of other highly obscured extragalactic objects, and of the class of "dark" GRBs in particular.
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