Center for Astrophysics and Space Astronomy

Boulder City, CO, United States

Center for Astrophysics and Space Astronomy

Boulder City, CO, United States
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Roseboom I.G.,University of Sussex | Roseboom I.G.,University of Edinburgh | Ivison R.J.,University of Edinburgh | Ivison R.J.,Astronomy Technology Center | And 91 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We investigate the potential of submm-mm and submm-mm-radio photometric redshifts using a sample of mm-selected sources as seen at 250, 350 and 500μm by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm sources with reliable radio identifications in the Great Observatories Origins Deep Survey North and Lockman Hole North fields, 46 (73per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm sources are adequately described by a modified blackbody with constant optical depth τ= (ν/nu 0) β, where β=+1.8 and ν 0=c/100μm. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation, we derive photometric redshift estimates for the 46 SPIRE-detected mm sources. Testing against the 22 sources with known spectroscopic or good quality optical/near-IR photometric redshifts, we find submm/mm photometric redshifts offer a redshift accuracy of |Δz|/(1 +z) = 0.16(〈|Δz|〉= 0.51). Including constraints from the radio-far-IR correlation, the accuracy is improved to |Δz|/(1 +z) = 0.15(〈|Δz|〉= 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z > 3 when compared to ∼ 850μm selected samples. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


Roseboom I.G.,University of Edinburgh | Roseboom I.G.,University of Sussex | Bunker A.,University of Oxford | Sumiyoshi M.,Kyoto University | And 43 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We investigate the properties (e.g. star formation rate, dust attenuation, stellar mass and metallicity) of a sample of infrared (IR) luminous galaxies at z ~ 1 via near-IR spectroscopy with Subaru-FMOS. Our sample consists of Herschel SPIRE and Spitzer MIPS selected sources in the COSMOS field with photometric redshifts in the range of 0.7 < z phot < 1.8, which have been targeted in two pointings (0.5 deg 2) with FMOS. We find a modest success rate for emission-line detections, with candidate Hα emission lines detected for 57 of 168 SPIRE sources (34 per cent). By stacking the near-IR spectra we directly measure the mean Balmer decrement for the Hα and Hβ lines, finding a value of 〈E(B - V)〉 = 0.51 ± 0.27 for 〈LIR〉 = 1012 L ⊙ sources at 〈z〉 = 1.36. By comparing star formation rates estimated from the IR and from the dust-uncorrected Ha line we find a strong relationship between dust attenuation and star formation rate. This relation is broadly consistent with that previously seen in star-forming galaxies at z ~ 0.1. Finally, we investigate the metallicity via the N2 ratio, finding that z ~ 1 IR-selected sources are indistinguishable from the local mass-metallicity relation. We also find a strong correlation between dust attenuation and metallicity, with the most metal-rich IR sources experiencing the largest levels of dust attenuation. © 2012 The Authors, Monthly Notices of the Royal Astronomical Society.


Perera T.A.,Illinois Wesleyan University | Wilson G.W.,University of Massachusetts Amherst | Scott K.S.,U.S. National Radio Astronomy Observatory | Austermann J.E.,Center for Astrophysics and Space Astronomy | And 2 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2013

A new technique for reliably identifying point sources in millimeter/submillimeter wavelength maps is presented. This method accounts for the frequency dependence of noise in the Fourier domain as well as nonuniformities in the coverage of a field. This optimal filter is an improvement over commonly-used matched filters that ignore coverage gradients. Treating noise variations in the Fourier domain as well as map space is traditionally viewed as a computationally intensive problem. We show that the penalty incurred in terms of computing time is quite small due to casting many of the calculations in terms of FFTs and exploiting the absence of sharp features in the noise spectra of observations. Practical aspects of implementing the optimal filter are presented in the context of data from the AzTEC bolometer camera. The advantages of using the new filter over the standard matched filter are also addressed in terms of a typical AzTEC map. © 2013. The Astronomical Society of the Pacific. All rights reserved.


Zavagno A.,French National Center for Scientific Research | Anderson L.D.,French National Center for Scientific Research | Russeil D.,French National Center for Scientific Research | Morgan L.,Liverpool John Moores University | And 17 more authors.
Astronomy and Astrophysics | Year: 2010

Context. It has been shown that by means of different physical mechanisms the expansion of H ii regions can trigger the formation of new stars of all masses. This process may be important to the formation of massive stars but has never been quantified in the Galaxy. Aims. We use Herschel-PACS and-SPIRE images from the Herschel infrared survey of the Galactic plane, Hi-GAL, to perform this study. Methods. We combine the Spitzer-GLIMPSE and-MIPSGAL, radio-continuum and submillimeter surveys such as ATLASGAL with Hi-GAL to study young stellar objects (YSOs) observed towards Galactic H ii regions. We select a representative H ii region, N49, located in the field centered on l = 30°observed as part of the Hi-GAL science demonstration phase, to demonstrate the importance Hi-GAL will have to this field of research. Results. Hi-GAL PACS and SPIRE images reveal a new population of embedded young stars, coincident with bright ATLASGAL condensations. The Hi-GAL images also allow us, for the first time, to constrain the physical properties of the newly formed stars by means of fits to their spectral energy distribution. Massive young stellar objects are observed at the borders of the N49 region and represent second generation massive stars whose formation has been triggered by the expansion of the ionized region. Conclusions. The first Hi-GAL images obtained using PACS and SPIRE have demonstrated the capability to investigate star formation triggered by H ii regions. With radio, submillimeter, and shorter wavelength infrared data from other surveys, the Hi-GAL images reveal young massive star-forming clumps surrounding the perimeter of the N49 H ii generated bubble. Hi-GAL enables us to detect a population of young stars at different evolutionary stages, cold condensations only being detected in the SPIRE wavelength range. The far IR coverage of Hi-GAL strongly constrains the physical properties of the YSOs. The large and unbiased spatial coverage of this survey offers us a unique opportunity to lead, for the first time, a global study of star formation triggered by H ii regions in our Galaxy. © 2010 ESO.


Loyd R.O.P.,Center for Astrophysics and Space Astronomy | France K.,Center for Astrophysics and Space Astronomy
Astrophysical Journal, Supplement Series | Year: 2014

Variations in stellar flux can potentially overwhelm the photometric signal of a transiting planet. Such variability has not previously been well-characterized in the ultraviolet lines used to probe the inflated atmospheres surrounding hot Jupiters. Therefore, we surveyed 38 F-M stars for intensity variations in four narrow spectroscopic bands: two enclosing strong lines from species known to inhabit hot Jupiter atmospheres, C II λλ1334, 1335 and Si III λ1206; one enclosing Si IV λλ1393, 1402; and 36.5 Å of interspersed continuum. For each star/band combination, we generated 60 s cadence lightcurves from archival Hubble Space Telescope Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph time-tagged photon data. Within these lightcurves, we characterized flares and stochastic fluctuations as separate forms of variability. Flares: we used a cross-correlation approach to detect 116 flares. These events occur in the time-series an average of once per 2.5 hr, over 50% last 4 minutes or less, and most produce the strongest response in Si IV. If the flare occurred during a transit measurement integrated for 60 minutes, 90/116 would destroy the signal of an Earth, 27/116 Neptune, and 7/116 Jupiter, with the upward bias in flux ranging from 1% to 109% of quiescent levels. Fluctuations: photon noise and underlying stellar fluctuations produce scatter in the quiescent data. We model the stellar fluctuations as Gaussian white noise with standard deviation σx. Maximum likelihood values of σx range from 1% to 41% for 60 s measurements. These values suggest that many cool stars will only permit a transit detection to high confidence in ultraviolet resonance lines if the radius of the occulting disk is ≳1 RJ. However, for some M dwarfs this limit can be as low as several R ⊕. © 2014. The American Astronomical Society. All rights reserved.

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