Early Science with the EVLA
Special Session | 217th American Astronomical Society Meeting |
Wednesday, January 12, 2011 | 10:00 AM PST
The Expanded Very Large Array (EVLA) is a major upgrade of the VLA, providing full frequency coverage from 1 to 50 GHz, up to 8 GHz of instantaneous bandwidth per polarization, and a new, Canadian-funded correlator that vastly increases the scientific capabilities of the array. The new WIDAR correlator will be able to provide full bandwidth coverage with full polarization and variable spectral resolution sufficient for virtually any scientific project.
The EVLA is now in its scientific commissioning phase. The new correlator is in place, processing data from all antennas, and is being used for regular science observations. The capabilities of the correlator are being rapidly increased, with a wide-band (2 GHz) mode available this summer, enabling new and original science.
In this special session, we will describe the current and future status of the EVLA, as it proceeds to its completion in 2012. The other speakers will present early science results from the observations made since the WIDAR correlator was turned on in March, with emphasis on those results arising from the wide-bandwidth capabilities enabled over the summer.
Session Chair, R. Perley (NRAO)
|10:05 A.M.||EVLA Observations of the Largest TNOs||Butler||Butler|
|10:17 A.M.||Grain Growth and Sub-Structure in Protoplanetary Disks||Chandler||Wilner (CfA)|
|10:29 A.M.||An EVLA Diagnostic K-Band Survey of Massive Young (Proto)stellar Objects||Brogan||Brogan|
|10:41 A.M.||Radio Continuum Emission from Classical Novae: eNova Project Early Results (and Surprises!)||Sokoloski||Krauss|
|10:53 A.M.||EVLA Constraints on the Progenitors of Supernovae Type Ia||Soderberg||Chomiuk (CfA)|
|11:05 A.M.||The Bimodal Luminosity Distribution of QSOs: Starbursts and AGN?||Kellermann||Kellermann|
|11:17 A.M.||Imaging molecular gas in primeval galaxies with the EVLA||Carilli||Carilli|
Authors: Crystal Brogan (NRAO), Todd Hunter (NRAO), Claudia Cyganowski (U. Wisconsin), Remy Indebetouw (U. Virginia), Claire Chandler (NRAO), Rachel Friesen (NRAO)
Abstract: We will present early results from a comprehensive study of 25 massive young stellar objects (MYSOs) at ~24 GHz (13mm) utilizing the power of the new EVLA WIDAR correlator to simultaneously observe the ammonia ladder through (6,6), the 25GHz methanol ladder, SO2, HC5N, recombination lines, and continuum at an angular resolution of ~10,000 AU. The selection criteria included: previous ammonia detections at (1,1) and (2,2), (sub)mm dust cores, a range of maser activity, and a range of 24micron luminosities and 8/24 micron colors. Together, the observed tracers provide the gas temperature, the frequency and strength of hot core emission, and the kinematics of cores, outflows, and ionized gas, all observed with a uniform sensitivity and resolution. With this wealth of data we aim to identify the best discriminators of MYSO evolutionary state, and ultimately better understand the process of massive star formation.
Authors: Bryan J. Butler (NRAO), Mark A. Gurwell (CfA), Arielle Moullet (CfA)
Abstract: Despite the importance of understanding TNOs in the context of solar system formation and evolution, the physical properties of these bodies are relatively poorly known. Though masses are known for at least those with satellites, their radii are poorly constrained, making estimates of such a fundamental quantity as density highly uncertain. Little is also known about the surface temperatures of these bodies; equilibrium with solar radiation is usually assumed.
Long wavelength thermal emission observations are a powerful way to constrain such quantities more accurately. They additionally sample below the surface (to roughly 10 wavelengths), yielding information about thermal and structure characteristics to that depth. Unfortunately, long wavelength emission is weak and has only been done successfully at millimeter wavelengths for a few of the largest TNOs.
The EVLA is the next generation centimeter wavelength telescope, building on the tremendous success of the VLA. The main improvement is an eventual factor of 10 better sensitivity. Observations at a wavelength of 1 cm of the TNOs 2002 TC302, Makemake, Quaoar, and Eris, along with the Pluto system and Triton have been approved for the EVLA, and we will present all data taken on these bodies. This is part of a longer term program to measure the microwave emission spectrum of these bodies from roughly 0.5 mm to 5 cm using both the EVLA and ALMA.
Authors: C. Carilli (NRAO), D. Riechers (Caltech), F. Walter (MPIA), J. Wagg (ESO), E. Daddi (Saclay), R. Wang (NRAO)
Abstract: The EVLA has opened a new window on the high redshift Universe through spatially and spectrally resolved imaging of the low order transitions from common molecules. These studies reveal the cool gas that fuels star formation in nascent galaxies. We will present the first results of CO imaging of distant galaxies with the EVLA during early science. These include: (i) two of the most distant extreme starburst (ie. submm) galaxies at z = 4.0 and 5.3, (ii) three near-IR selected star forming galaxies (sBzK) at z ~ 2, (iii) two strongly lensed Ly-break galaxies at z ~ 3, and (iv) three z ~ 6 quasar host galaxies. We derive total gas masses from the low order transitions, implying gas to stellar mass ratios of order unity in these early systems. A comparison with the higher order transitions shows evidence for extended, lower excitation molecular gas components in all cases besides the quasar hosts.
Authors: D. Wilner (CfA), C. Chandler (NRAO), S. Andrews (CfA), N. Calvet (U. Michigan), J. Carpenter (Caltech), S. Corder (NRAO), A. Deller (NRAO), C. Dullemond (MPIfA), J. Greaves (St. Andrews), T. Henning (MPIfA), A. Isella (Caltech), J. Lazio (JPL), H. Linz (MPIfA), L. Mundy (U. Maryland), L. Perez (Caltech), L. Ricci (ESO), A. Sargent (Caltech), S. Storm (U. Maryland), L. Testi (ESO)
Abstract: I will describe the Disks@EVLA program to survey protoplanetary disks around pre-main-sequence stars in the nearest star forming regions (Taurus, Ophiuchus, TW Hya) to investigate the millimeter/centimeter emission from large dust particles, the last observable link in the chain from sub-micron interstellar grains to planets. At these long wavelengths, dust emission is optically thin and probes the entire disk volume, including the innermost regions that become opaque in the submillimeter. Taking advantage of the new capabilities of the EVLA, we are using a staged approach that starts with photometry of approximately 60 disk systems, currently underway, to be followed by higher resolution imaging of smaller subsets of the brighter sources, ultimately reaching scales comparable to the orbital radius of Jupiter. Key goals include (1) determining the prevalence and location of grain growth to centimeter-sized "pebbles" from spectral indices, and any dependencies on stellar properties and environment, and (2) detecting physical sub-structures such as holes and gaps indicative of disk evolution and planet formation.
Authors: K. I. Kellermann, A. E. Kimball, J.J. Condon, R. Perley (NRAO); Z. Ivezic (University of Washington)
Abstract: In spite of nearly 50 years of study, it is still unclear whether or not the radio emission from QSOs is bimodal consisting of distinct radio loud and radio quiet populations. New 5 GHz EVLA observations exploit two recent developments: a) the availability of the recent DR7 SDSS to provide a volume limited sample of 197 confirmed QSOs (M< -23) within the narrow range 0.2 < z < 0.3; and b) the dramatic improvement in radio continuum sensitivity made possible by the increased bandwidth of the EVLA which lets us detect, with only 10 minutes of integration, a source as faint as L = 10^22 W/Hz, well below the value which separates star-forming galaxies from AGN. We report on early results from the EVLA on a sub set of our QSO sample. Previous studies have been limited by the inhomogeneity of the optical QSO sample, inadequate sensitivity to fully sample the radio quiet population, the degeneracy between redshift and luminosity for flux density limited samples, as well as by strong evolution over the wide range of observed redshifts.
Authors: Laura Chomiuk (Harvard-Smithsonian Center for Astrophysics), A. M. Soderberg (Harvard University), R. Chevalier (University of Virginia), C. Badenes (Tel Aviv University, Israel), C. Fransson (Stockholm University, Sweden)
Abstract: While Type Ia supernovae are used increasingly as cosmological probes to trace the expansion history of the Universe, the nature of their progenitors remains enshrouded in mystery. In the favored model for these explosions, a white dwarf accretes material from a hydrogen-rich donor star (e.g. red giant). A necessary implication of this model is the production of weak radio emission as the SN blastwave plows through the wind of the donor star. Previous radio searches for this signal have been unsuccessful, largely attributed to the fact that the expected emission lay just beyond the VLA sensitivity. Here we present recent results from our EVLA program, which utilizes the increased sensitivity to search for the expected signal from SNe Ia. The non-detection of radio emission with the EVLA would indicate double-degenerate progenitor systems (binary white dwarf) or require serious modifications to the single-degenerate model.
Authors: M. Krauss (NRAO), J. Sokoloski (Columbia), L. Chomiuk (NRAO), M. Rupen (NRAO), N. Roy (NRAO), G. Hallinan (National U. of Ireland, Galway), A. Mioduszewski (NRAO), M. Bode (Liverpool John Moores U.), S. Eyres (U. Central Lancashire), G. Knapp (Princeton U.), T. O'Brien (U. Manchester)
Abstract: We present initial results from the eNova Project, an EVLA campaign to observe nearby classical novae at early times with high-bandwidth, multi-frequency coverage. Because radio emission is not subject to extinction by dust, and because it remains optically thick at lower densities than optical emission, it is an ideal probe of the physical parameters of nova explosions. Simple models for radio light curves have historically been based on a picture in which thermal, ionized gas produces homogeneous, expanding ejecta. These models provided reasonable descriptions of previous radio data. However, this simplistic picture is incompatible with our EVLA observations of two novae --- V407 Cyg and V1723 Aql. We will discuss the discrepancies between the simple models and our new EVLA data, which promise to provide new information about the explosion, the ejecta, and the circum-binary environment.