Dr Aprajita Verma

Abstract:

We present high-resolution maps of stars, dust, and molecular gas in a strongly lensed submillimeter galaxy (SMG) at z = 3.259. HATLAS J114637.9-001132 is selected from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) as a strong lens candidate mainly based on its unusually high 500 μm flux density (300mJy). It is the only high-redshift Planck detection in the 130deg2 H-ATLAS Phase-I area. Keck Adaptive Optics images reveal a quadruply imaged galaxy in the K band while the Submillimeter Array and the Jansky Very Large Array show doubly imaged 880 μm and CO(1→0) sources, indicating differentiated distributions of the various components in the galaxy. In the source plane, the stars reside in three major kpc-scale clumps extended over 1.6kpc, the dust in a compact (∼1 kpc) region ∼3kpc north of the stars, and the cold molecular gas in an extended (∼7kpc) disk ∼5kpc northeast of the stars. The emissions from the stars, dust, and gas are magnified by ∼17, ∼8, and ∼7times, respectively, by four lensing galaxies at z ∼1. Intrinsically, the lensed galaxy is a warm (T dust ∼40-65 K), hyper-luminous (L IR ∼ 1.7 × 1013 L star formation rate (SFR) ∼2000 M yr-1), gas-rich (M gas/M baryon 70%), young (M stellar/SFR 20Myr), and short-lived (M gas/SFR 40Myr) starburst. With physical properties similar to unlensed z > 2 SMGs, HATLAS J114637.9-001132 offers a detailed view of a typical SMG through a powerful cosmic microscope. © 2012. The American Astronomical Society. All rights reserved..

Abstract:

We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 square degrees medium-deep survey at 3.6 and 4.5 microns with the post-cryogenic Spitzer Space Telescope to ~2 microJy (AB=23.1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from z~5 to the present day, and is the first extragalactic survey both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z>1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this paper, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicing to catalogs, as well as coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey.

Abstract:

Full range Herschel/PACS spectroscopy of the (ultra)luminous infrared galaxies NGC 4418 and Arp 220, observed as part of the SHINING key programme, reveals high excitation in H 2O, OH, HCN, and NH 3. In NGC 4418, absorption lines were detected with E lower > 800 K (H 2O), 600 K (OH), 1075 K (HCN), and 600 K (NH 3), while in Arp 220 the excitation is somewhat lower. While outflow signatures in moderate excitation lines are seen in Arp 220 as have been seen in previous studies, in NGC 4418 the lines tracing its outer regions are redshifted relative to the nucleus, suggesting an inflow with M ≲ 12 M yr -1. Both galaxies have compact and warm (T dust ≳ 100 K) nuclear continuum components, together with a more extended and colder component that is much more prominent and massive in Arp 220. A chemical dichotomy is found in both sources: on the one hand, the nuclear regions have high H 2O abundances, ∼10 -5, and high HCN/H 2O and HCN/NH 3 column density ratios of 0.1-0.4 and 2-5, respectively, indicating a chemistry typical of evolved hot cores where grain mantle evaporation has occurred. On the other hand, the high OH abundance, with OH/H 2O ratios of ∼0.5, indicates the effects of X-rays and/or cosmic rays. The nuclear media have high surface brightnesses (≳ 10 13 L⊙/kpc 2) and are estimated to be very thick (N H≳ 10 25 cm -2). While NGC 4418 shows weak absorption in H 218O and 18OH, with a 16O-to- 18O ratio of ≳ 250-500, the relatively strong absorption of the rare isotopologues in Arp 220 indicates 18O enhancement, with 16O-to- 18O of 70-130. Further away from the nuclear regions, the H 2O abundance decreases to ≲ 10 -7 and the OH/H 2O ratio is reversed relative to the nuclear region to 2.5-10. Despite the different scales and morphologies of NGC 4418, Arp 220, and Mrk 231, preliminary evidence is found for an evolutionary sequence from infall, hot-core like chemistry, and solar oxygen isotope ratio to high velocity outflow, disruption of the hot core chemistry and cumulative high mass stellar processing of 18O. © ESO, 2012.

Abstract:

We present the results of a gravitational lensing analysis of the bright z s = 2.957 submillimeter galaxy (SMG) HERMES found in the Herschel/SPIRE science demonstration phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high-resolution imaging available in optical and near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allows us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be μ = 10.9 ± 0.7. We measure the half-light radius R eff of the source in the rest-frame near-UV and V bands that characterize the unobscured light coming from stars and find R eff, * = [2.0 ± 0.1] kpc, in good agreement with recent studies on the SMG population. This lens model is also used to estimate the size of the gas distribution (Reff, gas = [1.1 ± 0.5] kpc) by mapping back in the source plane the CO (J = 5 → 4) transition line emission. The lens modeling yields a relatively large Einstein radius R Ein = 4.″10 ± 0″.02, corresponding to a deflector velocity dispersion of [483 ± 16] km s -1. This shows that HERMES is lensed by a galaxy group-size dark matter halo at redshift z l ∼ 0.6. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with f dm(< R Ein) ∼ 80%. This fraction reduces to f dm(< R eff, G1 ≃ 4.5 kpc) ∼ 47% within the effective radius of the main deflecting galaxy of stellar mass M *, G1 = [8.5 ± 1.6] × 1011 M ⊙. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at z ∼ 0.2 from the Sloan Lens ACS Survey. © 2011. The American Astronomical Society. All rights reserved.