7 research outputs found
HerMES: the rest-frame UV emission and a lensing model for the z= 6.34 luminous dusty starburst galaxy HFLS3
We discuss the rest-frame ultraviolet emission from the starbursting galaxy HFLS3 at a redshift of 6.34. The galaxy was discovered in Herschel/SPIRE data due to its red color in the submillimeter wavelengths from 250 to 500 ÎŒm. Keck/NIRC2 K s -band adaptive optics imaging data showed two potential near-IR counterparts near HFLS3. Previously, the northern galaxy was taken to be in the foreground at z = 2.1, while the southern galaxy was assumed to be HFLS3's near-IR counterpart. The recently acquired Hubble/WFC3 and Advanced Camera for Surveys (ACS) imaging data show conclusively that both optically bright galaxies are in the foreground at z < 6. A new lensing model based on the Hubble imaging data and the millimeter-wave continuum emission yields a magnification factor of 2.2 ± 0.3, with a 95% confidence upper limit on the magnification of 3.5. When corrected for lensing, the instantaneous star formation rate is 1320 M â yrâ1, with the 95% confidence lower limit around 830 M â yrâ1. The dust and stellar masses of HFLS3 from the same spectral energy distribution (SED) models are at the level of 3 Ă 108 M â and ~5 Ă 1010 M â, respectively, with large systematic uncertainties on assumptions related to the SED model. With Hubble/WFC3 images, we also find diffuse near-IR emission about 0.5 arcsec (~3 kpc) to the southwest of HFLS3 that remains undetected in the ACS imaging data. The emission has a photometric redshift consistent with either z ~ 6 or a dusty galaxy template at z ~ 2
Lensed galaxies in CANDELS
We present results from a search for gravitationally lensed galaxies present in the Hubble Space Telescope (HST)/Wide Field Camera-3 (WFC3) images of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). We present one bona fide lens system in UDS and two compact lens candidates in the GOODS-S field. The lensing system in UDS involves two background galaxies, one at z=1.847 lensed to an arc and a counterimage, and the second at a photometric redshift of z=2.32^{+0.10}_{-0.06} lensed to a double image. We reconstruct the lensed sources in the source plane and find in each of the two cases the sources can be separated to a pair of galaxies. The sources responsible for the arc are compact with effective radii of 0.3 to 0.4 kpc in WFC3 J_{125}-band and a total stellar mass and a star-formation rate of 2.1_{-0.4}^{+2.4} times 10^7 M_sun and 2.3_{-1.7}^{+ 0.6} M_sun yr^{-1}, respectively.The abnormally high H_{160}-band flux of this source is likely due to OIII emission lines with a rest-frame equivalent width about 700 Angstroms for OIII 5007 Angstroms. The sources responsible for the double image have corresponding values of about 0.4 to 0.5 kpc, 1.4_{-0.8}^{+1.9} times 10^9 M_sun, and 8.7_{-7.0}^{+11.1} M_sun yr^{-1}. Once completed CANDELS is expected to contain about 15 lensing systems and will allow statistical studies on both lensing mass profiles and z ~ 2 lensed galaxies
Multi-wavelength lens construction of a Planck and Herschel-detected star-bursting galaxy
We present a source-plane reconstruction of a Herschel and Planck-detected gravitationally lensed dusty star-forming galaxy (DSFG) at z = 1.68 using Hubble, Submillimeter Array (SMA), and Keck observations. The background submillimeter galaxy (SMG) is strongly lensed by a foreground galaxy cluster at z = 0.997 and appears as an arc with a length of âŒ15âł in the optical images. The continuum dust emission, as seen by SMA, is limited to a single knot within this arc. We present a lens model with source-plane reconstructions at several wavelengths to show the difference in magnification between the stars and dust, and highlight the importance of multi-wavelength lens models for studies involving lensed DSFGs. We estimate the physical properties of the galaxy by fitting the flux densities to model spectral energy distributions leading to a magnification-corrected starformation rate (SFR) of 390 ± 60 M yrâ1 and a stellar mass of 1.1 ± 0.4 10 x 11 M. These values are consistent with high-redshift massive galaxies that have formed most of their stars already. The estimated gas-to-baryon fraction, molecular gas surface density, and SFR surface density have values of 0.43 ± 0.13, 350 ± 200 M pcâ2, and ~ 12 7 M yrâ1 kpcâ2, respectively. The ratio of SFR surface density to molecular gas surface density puts this among the most star-forming systems, similar to other measured SMGs and local ULIRGs
Herschel-ATLAS and ALMA: HATLASâJ142935.3-002836, a lensed major merger at redshift 1.027
Context. The submillimetre-bright galaxy population is believed to comprise, aside from local galaxies and radio-loud sources, intrinsically active star-forming galaxies, the brightest of which are lensed gravitationally. The latter enable studies at a level of detail beyond what is usually possible by the observation facility.
Aims. This work focuses on one of these lensed systems, HATLASâJ142935.3â002836 (H1429â0028), selected in the Herschel-ATLAS field. Gathering a rich, multi-wavelength dataset, we aim to confirm the lensing hypothesis and model the background sourceâs morphology and dynamics, as well as to provide a full physical characterisation.
Methods. Multi-wavelength high-resolution data is utilised to assess the nature of the system. A lensing-analysis algorithm that simultaneously fits different wavebands is adopted to characterise the lens. The background galaxy dynamical information is studied by reconstructing the 3D source plane of the ALMA COâ(J:4âââ3) transition. Near-IR imaging from HST and Keck-AO allows to constrain rest-frame optical photometry independently for the foreground and background systems. Physical parameters (such as stellar and dust masses) are estimated via modelling of the spectral energy distribution taking source blending, foreground obscuration, and differential magnification into account.
Results. The system comprises a foreground edge-on disk galaxy (at zsp = 0.218) with an almost complete Einstein ring around it. The background source (at zsp = 1.027) is magnified by a factor of ÎŒ ~ 8â10 depending on wavelength. It is comprised of two components and a tens-of-kpc-long tidal tail resembling the AntennĂŠ merger. As a whole, the background source is a massive stellar system (1.32-0.41+ 0.63 Ă 1011 Mâ) forming stars at a rate of 394 ± 90â Mâ yr-1, and it has a significant gas reservoir MISM = 4.6 ± 1.7 Ă 1010 Mâ. Its depletion time due to star formation alone is thus expected to be ÏSF = MISM/ SFR = 117 ± 51 Myr. The dynamical mass of one of the components is estimated to be 5.8 ± 1.7 Ă 1010 Mâ, and, together with the photometric total mass estimate, it implies that H1429â0028 is a major merger system (1:2.8-1.5+1.8)
The Study of Dusty Star-Forming Galaxies Through Far-Infrared Observations
In this thesis I use far-infrared (far-IR) observations performed by the Herschel Space Observatory to study dusty star-forming galaxies, which are believed to be the likely progenitors of massive elliptical galaxies. More specifically, I investigate the far-IR emission of dust-obscured galaxies (DOGs), analyze the near-IR imaging of Herschel-selected lensed galaxies, and investigate the rest-frame UV emission of HFLS3, a z=6.34 Herschel-selected starburst
Extinction and nebular line properties of a Herschel-selected lensed dusty starburst at z = 1.027
We present Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging and grism spectroscopy observations of the Herschel-selected gravitationally lensed starburst galaxy HATLASJ1429-0028. The lensing system consists of an edge-on foreground disk galaxy at z = 0.218 with a nearly complete Einstein ring of the infrared luminous galaxy at z = 1.027. The WFC3 spectroscopy with G102 and G141 grisms, covering the wavelength range of 0.8â1.7 ÎŒm, resulted in detections of Hα + [Nii], HÎČ, [Sii], and [Oiii] for the background galaxy from which we measure line fluxes and ratios. The Balmer line ratio Hα/HÎČ of 7.5 ± 4.4, when corrected for [Nii], results in an extinction for the starburst galaxy of . The Hα-based star formation rate (SFR), when corrected for extinction, is 60 ± 50 yrâ1, lower than the instantaneous SFR of 390 ± 90 yrâ1 from the total IR luminosity. We also compare the nebular line ratios of HATLASJ1429-0028 with other star-forming and sub-millimeter bright galaxies. The nebular line ratios are consistent with an intrinsic ultra-luminous infrared galaxy with no evidence for excitation by an active galactic nucleus (AGN). We estimate the metallicity, 12 + log(O/H), of HATLASJ1429-0028 to be 8.49 ± 0.16. Such a low value is below the average relation for stellar mass versus metallicity of galaxies at for a galaxy with a stellar mass of . The combination of high stellar mass, the lack of AGN indicators, low metallicity, and the high SFR of HATLASJ1429-0028 suggest that this galaxy is currently undergoing a rapid formation
Student Scientific Research within Communities-of-Practice
Social learning theory suggests that students who wish to become scientists will benefit by being active researchers early in their educational careers. As coauthors of published research, they identify themselves as scientists. This provides them with the inspiration, motivation, and staying power that many will need to complete the long educational process. This hypothesis was put to the test over the past decade by a one-semester astronomy research seminar where teams of students managed their own research. Well over a hundred
published papers coauthored by high school and undergraduate students at a handful of schools substantiated this hypothesis. However, one could argue that this was a special case. Astronomy, after all, is supported by a large professional-amateur community-of-practice. Furthermore, the specific area of researchâdouble star astrometryâwas chosen because the observations could be quickly made, the data reduction and analysis was straight forward, and publication of the research was welcomed by the Journal of Double Star Observations. A recently initiated seminar development and expansion programâsupported in part by the National Science Foundationâis testing a more general hypothesis that: (1) the seminar can be successfully adopted by many
other schools; (2) research within astronomy can be extended from double star astrometry to time series
photometry of variable stars, exoplanet transits, and asteroids; and (3) the seminar model can be extended to a
science beyond astronomy: environmental scienceâspecifically atmospheric science. If the more general
hypothesis is also supported, seminars that similarly feature published high school and undergraduate studen