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RISS 인기검색어
- 검색키워드
- 저자 : Scoville, N. (검색결과 5 건)
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STARBURST AND AGN CONNECTIONS AND MODELS
SCOVILLE NICK The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.3
There is accumulating evidence for a strong link between nuclear starbursts and AGN. Molecular gas in the central regions of galaxies plays a critical role in fueling nuclear starburst activity and feeding central AGN. The dense molecular ISM is accreted to the nuclear regions by stellar bars and galactic interactions. Here we describe recent observational results for the OB star forming regions in M51 and the nuclear star burst in Arp 220 - both of which have approximately the same rate of star formation per unit mass of ISM. We suggest that the maximum efficiency for forming young stars is an Eddington-like limit imposed by the radiation pressure of newly formed stars acting on the interstellar dust. This limit corresponds to approximately 500 $L_{\bigodot} / M_{\bigodot}$ for optically thick regions in which the radiation has been degraded to the NIR. Interestingly, we note that some of the same considerations can be important in AGN where the source of fuel is provided by stellar evolution mass-loss or ISM accretion. Most of the stellar mass-loss occurs from evolving red giant stars and whether their mass-loss can be accreted to a central AGN or not depends on the radiative opacity of the mass-loss material. The latter depends on whether the dust survives or is sublimated (due to radiative heating). This, in turn, is determined by the AGN luminosity and the distance of the mass-loss stars from the AGN. Several AGN phenomena such as the broad emission and absorption lines may arise in this stellar mass-loss material. The same radiation pressure limit to the accretion may arise if the AGN fuel is from the ISM since the ISM dust-to-gas ratio is the same as that of stellar mass-loss.
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THE HST COSMOS PROJECT: CONTRIBUTION FROM THE SUBARU TELESCOPE
TANIGUCHI YOSHIAKI,SCOVILLE N. Z.,SANDERS D. B.,MOBASHER B.,AUSSEL H.,CAPAK P.,AJIKI M.,MURAYAMA T.,MIYAZAK S.,KOMIYAMA Y.,SHIOYA Y.,NAGAO T. The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2
The Cosmic Evolution Survey (COSMOS) is a Hubble Space Telescope (HST) treasury project. The COSMOS aims to perform a 2 square degree imaging survey of an equatorial field in I(F814W) band, using the Advanced Camera for Surveys (ACS). Such a wide field survey, combined with ground-based photometric and spectroscopic data, is essential to understand the interplay between large scale structure, evolution and formation of galaxies and dark matter. In 2004, we have obtained high-quality, broad band images of the COSMOS field (B, V, r', i', and z') using Suprime-Cam on the Subaru Telescope, and we have started our new optical multi-band program, COSMOS-21 in 2005. Here, we present a brief summary of the current status of the COSMOS project together with contributions from the Subaru Telescope. Our future Subaru program, COSMOS-21, is also discussed briefly.
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AzTEC millimetre survey of the COSMOS field – I. Data reduction and source catalogue
Scott, K. S.,Austermann, J. E.,Perera, T. A.,Wilson, G. W.,Aretxaga, I.,Bock, J. J.,Hughes, D. H.,Kang, Y.,Kim, S.,Mauskopf, P. D.,Sanders, D. B.,Scoville, N.,Yun, M. S. Blackwell Publishing Ltd 2008 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.385 No.4
<P>ABSTRACT</P><P>We present a 1.1 mm wavelength imaging survey covering 0.3 deg<SUP>2</SUP> in the COSMOS field. These data, obtained with the AzTEC continuum camera on the James Clerk Maxwell Telescope, were centred on a prominent large-scale structure overdensity which includes a rich X-ray cluster at <I>z</I>≈ 0.73. A total of 50 mm-galaxy candidates, with a significance ranging from 3.5 to 8.5σ, are extracted from the central 0.15 deg<SUP>2</SUP> area which has a uniform sensitivity of ∼1.3 mJy beam<SUP>−1</SUP>. 16 sources are detected with S/N ≥ 4.5, where the expected false-detection rate is zero, of which a surprisingly large number (9) have intrinsic (deboosted) fluxes ≥5 mJy at 1.1 mm. Assuming the emission is dominated by radiation from dust, heated by a massive population of young, optically obscured stars, then these bright AzTEC sources have far-infrared luminosities >6 × 10<SUP>12</SUP> L<SUB>⊙</SUB> and star formation rates >1100 M<SUB>⊙</SUB> yr<SUP>−1</SUP>. Two of these nine bright AzTEC sources are found towards the extreme peripheral region of the X-ray cluster, whilst the remainder are distributed across the larger scale overdensity. We describe the AzTEC data reduction pipeline, the source-extraction algorithm, and the characterization of the source catalogue, including the completeness, flux deboosting correction, false-detection rate and the source positional uncertainty, through an extensive set of Monte Carlo simulations. We conclude with a preliminary comparison, via a stacked analysis, of the overlapping MIPS 24-μm data and radio data with this AzTEC map of the COSMOS field.</P>
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Austermann, J. E.,Aretxaga, I.,Hughes, D. H.,Kang, Y.,Kim, S.,Lowenthal, J. D.,Perera, T. A.,Sanders, D. B.,Scott, K. S.,Scoville, N.,Wilson, G. W.,Yun, M. S. Blackwell Publishing Ltd 2009 Monthly notices of the Royal Astronomical Society Vol.393 No.4
<P>ABSTRACT</P><P>We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg<SUP>2</SUP> AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at <I>z</I>≲ 1.1. This portion of the COSMOS field shows a ∼3σ overdensity of robust SMG detections when compared to a background, or ‘blank-field’, population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes <I>S</I><SUB>1.1 mm</SUB> > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an overdensity significance of ≫ 4σ. We find that the overdensity and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the <I>z</I>≲ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the survey region, and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.</P>
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