Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm
Galactic & Extra-Galactic Star Formation
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130Galactic & Extra-Galactic Star FormationPoster SessionEssex Ballroom130.01
Spatially Resolved Molecular Gas Star Formation Law in CARMA Survey Towards Infrared-bright Nearby Galaxies (STING) Nurur Rahman1, A. Bolatto1, STING collaboration 1University of Maryland. 8:00 AM - 7:00 PM Essex Ballroom The STING is a CARMA 3mm survey of nearby galaxies. We will present a comprehensive analysis of the relationship between the star formation rate surface density and molecular gas surface at the sub-kpc level in the STING sample. To construct the tracers of molecular gas and star formation rate surface densities, respectively, we will use high resolution (3-5") CO (J=1-0) data from CARMA and the mid-infrared 24 micron data of comparable resolution (6") from Spitzer Space Telescope. We measure the relation in the bright region of these galaxies. In our preliminary analysis we find an approximately linear relation and no strong trends for either the logarithmic slope or the molecular depletion time across the range of galaxy masses sampled (10^9-10^11.5 Msun). 130.02
Star Formation Rates in Galaxy Groups in COSMOS Stephanie Fiorenza1 1CUNY Graduate Center. 8:00 AM - 7:00 PM Essex Ballroom This study examines the star formation rates within a sample of groups selected from the Cosmic Evolution Survey (COSMOS), a 2 deg2 multi-wavelength imaging and spectroscopic survey from x-ray to radio wavelengths. Of the roughly 1,000,000 objects within the COSMOS survey, ~20,000 currently have secure spectroscopic redshifts. The sample of galaxy groups is selected from x-ray data and has been spectroscopically confirmed. The sample encompasses more than 100 galaxy groups with a mass range of 1013 - 1015 solar masses and a redshift range of 0.1 ≥ z ≥ 1. Stellar mass fraction has previously been found to be anti-correlated with total mass, with clusters having lower stellar mass fractions than groups, while gas mass has been found to be positively correlated with total system mass. I investigate if star formation is a process that could significantly account for these and other observed properties of galaxy groups and the intra-group medium. Assuming representative initial-mass functions, I measure the total and specific star formation rates in the group galaxies. These results can be further applied to determine if the feedback from star formation can account for the observed baryon deficit observed within intra-group media, perhaps by blowing the baryonic interstellar gas out of the groups. 130.03
The Star Formation Reference Survey -- Survey Design and Basic Data Matthew Ashby1, S. Mahajan1, H. A. Smith1, S. Willner1, G. G. Fazio1, S. Raychaudhury2, A. Zezas3, P. Barmby4, P. Bonfini3, C. Cao5, E. Gonzalez-Alfonso6, D. Ishihara7, H. Kaneda7, V. Lyttle4, S. Madden8, C. Papovich9, E. Sturm10, J. Surace11, H. Wu12, Y. Zhu12 1SAO, 2University of Birmingham, United Kingdom, 3University of Crete, Greece, 4University of Western Ontario, Canada, 5Shandong University at Weihai, China, 6University de Alcala de Henares, Spain, 7Nagoya University, Japan, 8CEA/Saclay, France, 9Texas A & M University, 10MPE, Germany, 11Spitzer Science Center, 12National Astronomical Observatories, China. 8:00 AM - 7:00 PM Essex Ballroom We report on the survey design, available data, and first outcomes from the Star Formation Reference Survey, a program designed to systematically elucidate the properties of star forming galaxies. By controlling for both total and specific star formation rate together with dust temperature, we have assembled a large infrared-selected galaxy sample that is fully representative of all conditions under which star formation occurs in the local Universe. A rich dataset spanning multiple bands from the UV to the mid-IR and into the radio is now being used to assess the reliabilty and systematics of the star formation rate indicators commonly used in the literature, with an eye toward establishing a firmer baseline for the interpretation of faint, distant sources from deep infrared surveys. This work was supported by NASA grant number 1256790, administered by JPL. 130.04
Young Stellar Populations in the W3 Star-Forming Region Megan Bagley1, J. Jose2, J. S. Kim1, M. Bagley1, M. R. Meyer3, W. Sherry4, V. Roccatagliata5, L. Townsley6, E. Feigelson6 1University of Arizona, 2ARIES, India, 3ETH, Switzerland, 4NOAO/NSO, 5STScI, 6Pennsylvania State University. 8:00 AM - 7:00 PM Essex Ballroom We present recent results and updates from our multi-wavelength imaging and spectroscopic studies of young stars in the W3 star-forming complex and the surrounding area including IC 1795, W3 North, W3(OH), W3 Main, W3 South, and AFGL 333. We introduce newly-found embedded clusters and aggregates in W3 South and AFGL 333. The W3/W4/W5 complexes are well-known sites of massive star formation and are ideal sites to study the triggered mode of star formation. We conducted a systematic imaging and spectroscopic survey to study the initial mass function and the evolution of circumstellar disks in such an environment. We obtained optical imaging data and spectra with the 90 Prime on the Bok telescope and the Hectospec on the MMT, respectively, and we also made use of archival infrared data from 2MASS and Spitzer and X-ray data from Chandra. We present spectroscopically confirmed young stars and discuss their stellar properties. Using improved determinations of stellar ages and masses, we analyse the circumstellar disk frequency and the disk properties of young stars for M > ~0.8 Msun. 130.05
On the Initial Conditions for Star Formation and the IMF Bruce Elmegreen1 1IBM Research Div.. 8:00 AM - 7:00 PM Essex Ballroom Density probability distribution functions (PDFs) for turbulent self-gravitating clouds should be convolutions of the local log-normal PDF, which depends on the local average density rho-ave and Mach number M, and the probability distribution functions for rho-ave and M, which depend on the overall cloud structure. When self-gravity drives a cloud to increased central density, the total PDF develops an extended tail. If there is a critical density or column density for star formation, then the fraction of the local mass exceeding this threshold becomes higher near the cloud center. These elements of cloud structure should be in place before significant star formation begins. Then the efficiency is high so that bound clusters form rapidly, and the stellar initial mass function (IMF) has an imprint in the gas before destructive radiation from young stars can erase it. The IMF could arise from a power-law distribution of mass for cloud structure. These structures should form stars down to the thermal Jeans mass MJ at each density in excess of a threshold. The high-density tail of the PDF, combined with additional fragmentation in each star-forming core, extends the IMF into the Brown Dwarf regime. The core fragmentation process is distinct from the cloud structuring process and introduces an independent core fragmentation mass function (CFMF). The CFMF would show up primarily below the IMF peak. 130.06
A Search for Triggered Star Formation William Joseph Dirienzo1, R. Indebetouw2, C. Brogan3 1University of Virginia, 2University of Virginia/National Radio Astronomy Observatory, 3National Radio Astronomy Observatory. 8:00 AM - 7:00 PM Essex Ballroom A study was conducted to search for evidence of triggered star formation in six galactic H II regions with suggestive “bubble” morphology in a range of apparent evolutionary states. Young Stellar Objects (YSOs) in these regions were identified from the GLIMPSE point source catalog. Photometric data covering 1.25 μm to 24 μm wavelengths with the 2MASS survey and the Spitzer Space Telescope GLIMPSE and MIPSGAL surveys (utilizing the IRAC and MIPS instruments, respectively) was obtained for each source. The identification was performed by fitting the spectral energy distributions of each source with a collection of previously published YSO radiative transfer models. This method allows for an estimate of each YSO’s physical characteristics from the parameters of the models, including mass, luminosity, evolutionary stage, and age. The physical environments were analyzed using CO data from the Boston University Galactic Ring Survey and radio continuum data from the VLA Galactic Plane Survey and the Nobeyama 3 cm Survey. The ages of the H II regions are estimated from the physical characteristics of the region. Finally, the spatial distribution of YSOs and the timescales of YSO formation and H II region expansion are assessed for consistency or discrepancy with the collect and collapse and radiatively driven implosion models of triggered star formation. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. 130.07
Interactions Between Forming Stars and Dense Gas in a Small Low Mass Cluster Edwin F. Ladd1, T. Wong2, T. L. Bourke3, K. L. Thompson4 1Bucknell Univ., 2University of Illinois, 3Harvard-Smithsonian Center for Astrophysics, 4University of Kentucky. 8:00 AM - 7:00 PM Essex Ballroom We present observations of dense gas and outflow activity in the Cederblad 110 region of the Chamaleleon I Dark Cloud. The region contains eight forming low mass stars in evolutionary stages ranging from Class 0 to Class II/III crowded into a 0.2 pc region with high surface density (Σ_YSO ~150 pc^-2). The analysis of our N2H+ (J=1-0) maps indicates the presence of 15 solar masses of dense (n ~10^5 cm^-3) gas in this region, much of which is unstable against gravitational collapse. The most unstable material is located near the Class 0 source MMS 1. Smaller column densities of more stable dense gas are found toward the region's Class I sources. Little or no dense gas is colocated with the Class II and III sources in the region. The outflow from the Class I source IRS 4 is interacting with the dense core associated with MMS 1. The molecular component of the outflow appears to be deflected by the densest part of the core, after which it plows through some of the lower column density portions of the core. The working surface at the head of the outflow lobe can be seen in the enhanced velocity dispersion of the dense gas. The Class III source IRS 2 may also be influencing the dense gas in the region. A dust temperature gradient across the core is consistent with warming from the 3.4 Lo source, and a sharp gradient in dense gas column density may be caused by winds from this source. Taken together, our data indicate that this region has been producing several young stars in the recent past, and that sources which began forming first are interacting with the remaining dense gas in the region, thereby influencing current and future star formation activity. 130.08
New Data for Five New Orion PMS Eclipsing Binaries from the Spitzer YSOVAR Program. Maria Morales-Calderon1, J. R. Stauffer1, L. Prato2, L. A. Hillenbrand1, D. Terndrup3, S. Terebey4, L. M. Rebull1, K. Stassun5, A. Boden6 1CALTECH, 2Lowell Observatory, 3Ohio State University, 4California State University at Los Angeles, 5Vanderbilt University, 6Palomar Observatory - CALTECH. 8:00 AM - 7:00 PM Essex Ballroom In Fall 2009, we conducted a large, multi-wavelength time-series photometric monitoring campaign of about a one square degree region of the Orion Nebula cluster (ONC). From these data we identify nine stars in our field of view whose light curves show eclipse features. Four of these are the previously known ONC eclipsing binaries (EBs) and the other five systems are newly identified ONC PMS EB candidates - more than doubling what was known up to now. Here we present our follow-up observations and current work to confirm these candidates. 130.09
8:00 AM - 7:00 PM Essex Ballroom Using Spitzer Space Telescope and Chandra X-ray data, we identify YSOs in the RMC main core region. Nearest Neighbor Method (NNM) was employed to analyze the structures and distributions of Class I/0, Class II, and Class III sources. Additionally, we developed a ratio mapping technique to investigate the progression of star formation. We discuss the distribution of YSOs, progression of star formation, and structure of the clusters in this region. This work is based in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by an award issued by JPL/Caltech, Florida Space Grant Consortium, and a NASA GSRP fellowship. 130.10
Outflows, Hot-core And Magnetic Fields In G30.79fir10 Tirupati K. Sridharan1 1Harvard-Smithsonian CfA. 8:00 AM - 7:00 PM Essex Ballroom We present spectral line and dust polarization observations of G30.79FIR10 also known as W43-mm1, the brightest dust emission core in W43. The data were obtained with the Submillimeter Array (SMA) at ~ 345 GHz. Massive, jet-like outflows are observed in CO. A remarkable hot core with CH3CN (J=19-18) emission detected up to K = 10 and a temperature of ~ 300K is revealed. The magnetic field implied by the polarized dust emission is discussed. 130.11
8:00 AM - 7:00 PM Essex Ballroom The chemical makeup of Infrared Dark Clouds may offer a method to classify star forming cores. This study uses the molecular line maps from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey, observed using the 22-m ATNF Mopra Telescope. The relative abundances of the four molecules, N2H+, HNC, HCN and HCO+ are calculated for each of 500 cores to determine the chemical signatures of star forming cores in their early evolutionary stages, as deduced from Spitzer data. Cores are classified as prestellar, protostellar, or HII regions. Initial findings indicate that sources with relatively strong N2H+ lines are prestellar, whereas weak N2H+ lines may designate protostellar or HII regions. These chemical anomalies, where the N2H+ lines are either very prominent or weak are rare, suggesting that these are short-lived chemical phases. 130.12
8:00 AM - 7:00 PM Essex Ballroom We present combined CARMA and FCRAO 12CO(1-0), 13CO(1-0), and C18O(1-0) emission line maps of the Serpens Core as well as 2.7 mm continuum images from CARMA alone. The maps sample spatial scales from 5" up to 10' (2000 AU to >1 pc). The Serpens Core is a dynamic, active star-forming region. Several remarkable features are revealed in the combined maps including outflows, shells, remnant cavities from outflows, and filaments. The continuum maps are remarkably sparse despite the presence of extended, dense gas as traced by the C18O emission. We are in the process of cataloging the energy injecting sources. In later analysis we will determine the power spectra of velocity and density fluctuations in the field to compare to models of star formation as well as determine the influence of these energetic source on the surrounding medium. The CARMA maps are part of a three-region survey of large (75-150 pointing) mosaics that includes Perseus B1 and NGC 1333. 130.13
8:00 AM - 7:00 PM Essex Ballroom We have observed 37 Infrared Dark Clouds (IRDCs) containing a total of 159 clumps with the 22-meter ATNF Mopra Telescope in Australia using high-density molecular tracers at 3 mm. We carried out single-pointing observations in the broad-band mode and detected 10 different molecular lines. The detections rates are dominated by HNC (1-0) (98%), N2H+ (1-0) (97%), and HCO+ (1-0) (88%) lines, showing similar values when we divide the sample into active and quiescent clumps (based on Spitzer IRAC and MIPS emission). However, we find differences of ~30% in the detection rates for the H13CO+, HN13C, and HC3N lines. We also find that the N2H+ FWHMs of active clumps are broader than those of quiescent clumps, possibly due to ongoing star formation activity driving turbulence. Integrated intensity and abundance ratios of some molecular lines vary between quiescent and active clumps tracing chemical differences which arise from different evolutionary states. 130.14
30 Dorados & the Sinusoidal Potential David F. Bartlett1, J. P. Cumalat1 1Univ. of Colorado. 8:00 AM - 7:00 PM Essex Ballroom The sinusoidal potential is an alternative to the Newtonian potential. In this alternative, the potential of a point mass is φ= -(GM/r) Cos[kor], where ko = 2π/ λo and λo is determined empirically to be Ro/20, Ro=8 kpc. A parallel modification to electromagnetism has also been suggested φ=-(Q/r) Exp -[kor] (Bartlett 2004). Recently an equivalent absolute value for ko has been posited: ko2= πG (α 2 me) 4 c/ (h-bar)3. The sinusoidal potential has been developed in presentations at many recent meetings of the AAS & the DDA. Generally, short-range structure (galaxies and smaller) are dominated by gravitation; long-range (clusters of galaxies and larger) by electromagnetism. 30 Dorados is still a puzzle. Why should this region of intense star formation be between the Large Magellanic Cloud and the Milky Way, but much closer to the former than the latter. Why should its size be roughly 400 pc? What is its connection to the Magellanic Stream? The sinusoidal potential may help. Download 2.63 Mb. Share with your friends:
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