Dr Aprajita Verma

Abstract:

We present high-spatial resolution imaging obtained with the Submillimeter Array (SMA) at 880 μm and the Keck adaptive optics (AO) system at the K S-band of a gravitationally lensed submillimeter galaxy (SMG) at z = 4.243 discovered in the Herschel Astrophysical Terahertz Large Area Survey. The SMA data (angular resolution 06) resolve the dust emission into multiple lensed images, while the Keck AO K S-band data (angular resolution 01) resolve the lens into a pair of galaxies separated by 03. We present an optical spectrum of the foreground lens obtained with the Gemini-South telescope that provides a lens redshift of z lens = 0.595 ± 0.005. We develop and apply a new lens modeling technique in the visibility plane that shows that the SMG is magnified by a factor of μ = 4.1 ± 0.2 and has an intrinsic infrared (IR) luminosity of L IR = (2.1 ± 0.2) × 1013 L ⊙. We measure a half-light radius of the background source of r s = 4.4 ± 0.5kpc which implies an IR luminosity surface density of ΣIR = (3.4 ± 0.9) × 1011 L ⊙kpc-2, a value that is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at z 0. The two lens galaxies are compact (r lens 0.9kpc) early-types with Einstein radii of θE1 = 0.57 ± 0.01 and θE2 = 0.40 ± 0.01 that imply masses of M lens1 = (7.4 ± 0.5) × 1010 M ⊙ and M lens2 = (3.7 ± 0.3) × 10 10 M ⊙. The two lensing galaxies are likely about to undergo a dissipationless merger, and the mass and size of the resultant system should be similar to other early-type galaxies at z 0.6. This work highlights the importance of high spatial resolution imaging in developing models of strongly lensed galaxies discovered by Herschel. © 2012. The American Astronomical Society. All rights reserved.

Abstract:

We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14-30 (E upper/kB = 580-2565K) range, all of which are consistent with arising from within the central 10″ (700pc). The detected transitions are modeled as arising from two different components: a moderate-excitation (ME) component close to the galaxy systemic velocity and a high-excitation (HE) component that is blueshifted by 80kms-1. We employ a large velocity gradient model and derive n H2 105.6cm-3, T kin 170K, and M H2 106.7 M ⊙ for the ME component and n H2 106.4cm-3, T kin 570K, and M H2 105.6 M ⊙ for the HE component, although for both components the uncertainties in the density and mass are ±(0.6-0.9)dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution and find that the ME transitions are consistent with these lines arising in the200pc diameter ring of material traced by H 2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H2 ring, but a better kinematic match is found with a clump of infalling gas 40pc north of the active galactic nucleus (AGN). We consider potential heating mechanisms and conclude that X-ray- or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN and conclude that while the moderate thermal pressure precludes an association with the 1pc radius H2O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN and might then provide the N H 1025cm-2 column obscuring the nuclear hard X-rays. Finally, we also report sensitive upper limits extending up to J upper = 50, which place constraints on a previous model prediction for the CO emission from the X-ray obscuring torus. © 2012 The American Astronomical Society. All rights reserved.

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.