A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre ...HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich (Mdust≃ 9 × 108M⊙), luminous (LFIR≃ 2 × 1012L⊙) star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of ≃400 M⊙ yr−1. We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N350(>25 mJy) ∼ 200–500 deg−2.
We present an implementation of a blind source separation algorithm to remove foregrounds off millimeter surveys made by single-channel instruments. In order to make possible such a decomposition ...over single-wavelength data, we generate levels of artificial redundancy, then perform a blind decomposition, calibrate the resulting maps, and lastly measure physical information. We simulate the reduction pipeline using mock data: atmospheric fluctuations, extended astrophysical foregrounds, and point-like sources, but we apply the same methodology to the Aztronomical Thermal Emission Camera/ASTE survey of the Great Observatories Origins Deep Survey-South (GOODS-S). In both applications, our technique robustly decomposes redundant maps into their underlying components, reducing flux bias, improving signal-to-noise ratio, and minimizing information loss. In particular, GOODS-S is decomposed into four independent physical components: one of them is the already-known map of point sources, two are atmospheric and systematic foregrounds, and the fourth component is an extended emission that can be interpreted as the confusion background of faint sources.
We present a high-sensitivity (1 < 1.6 mJy beam−1) continuum observation in a 343 arcmin2 area of the northeast region of the Small Magellanic Cloud at a wavelength of 1.1 mm, conducted using the ...AzTEC instrument on the ASTE telescope. In the observed region, we identified 20 objects by contouring 10 emission. Through spectral energy distribution analysis using 1.1 mm, Herschel, and Spitzer data, we estimated gas masses of 5 × 103-7 × 104 M , assuming a gas-to-dust ratio of 1000. The dust temperature and index of emissivity were also estimated as 18-33 K and 0.9-1.9, respectively, which are consistent with previous low-resolution studies. The dust temperature and the index of emissivity shows a weak negative linear correlation. We also investigated five CO-detected, dust-selected clouds in detail. The total gas masses were comparable to those estimated from the Mopra CO data, indicating that the assumed gas-to-dust ratio of 1000 and the XCO factor of 1 × 1021 cm−2 (K km s−1)−1, with uncertainties of a factor of 2, are reliable for the estimation of the gas masses of molecular or dust-selected clouds. The dust column density showed good spatial correlation with CO emission, except for an object associated with bright young stellar objects. The 8 m filamentary and clumpy structures also showed a spatial distribution similar to that of the CO emission and dust column density, supporting the fact that polycyclic aromatic hydrocarbon emissions arise from the surfaces of dense gas and dust clouds.
ID11 is an actively star-forming, extremely compact galaxy and Lyα emitter at z = 3.117 that is gravitationally magnified by a factor of ~17 by the cluster of galaxies Hubble Frontier Fields AS1063. ...The observed properties of this galaxy resemble those of low luminosity HII galaxies or giant HII regions such as 30 Doradus in the Large Magellanic Cloud. Using the tight correlation correlation between the Balmer-line luminosities and the width of the emission lines (typically L(Hβ) − σ(Hβ)), which are valid for HII galaxies and giant HII regions to estimate their total luminosity, we are able to measure the lensing amplification of ID11. We obtain an amplification of 23 ± 11 that is similar within errors to the value of ~17 estimated or predicted by the best lensing models of the massive cluster Abell S1063. We also compiled, from the literature, luminosities and velocity dispersions for a set of lensed compact star-forming regions. There is more scatter in the L−σ correlation for these lensed systems, but on the whole the results tend to support the lensing model estimates of the magnification. Our result indicates that the amplification can be independently measured using the L − σ relation in lensed giant HII regions or HII galaxies. It also supports the suggestion, even if lensing is model dependent, that the L − σ relation is valid for low luminosity high-z objects. Ad hoc observations of lensed star-forming systems are required to determine the lensing amplification accurately.
On the Clustering of Submillimeter Galaxies Williams, Christina C; Giavalisco, Mauro; Porciani, Cristiano ...
Astrophysical journal/The Astrophysical journal,
06/2011, Letnik:
733, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We measure the angular two-point correlation function of submillimeter galaxies (SMGs) from 1.1 mm imaging of the COSMOS field with the AzTEC camera and ASTE 10 m telescope. These data yield one of ...the largest contiguous samples of SMGs to date, covering an area of 0.72 deg2 down to a 1.26 mJy beam--1 (1 Delta *s) limit, including 189 (328) sources with S/N >=3.5 (3). We can only set upper limits to the correlation length r 0, modeling the correlation function as a power law with pre-assigned slope. Assuming existing redshift distributions, we derive 68.3% confidence level upper limits of r 0 6-8h --1 Mpc at 3.7 mJy and r 0 11-12 h --1 Mpc at 4.2 mJy. Although consistent with most previous estimates, these upper limits imply that the real r 0 is likely smaller. This casts doubts on the robustness of claims that SMGs are characterized by significantly stronger spatial clustering (and thus larger mass) than differently selected galaxies at high redshift. Using Monte Carlo simulations we show that even strongly clustered distributions of galaxies can appear unclustered when sampled with limited sensitivity and coarse angular resolution common to current submillimeter surveys. The simulations, however, also show that unclustered distributions can appear strongly clustered under these circumstances. From the simulations, we predict that at our survey depth, a mapped area of 2 deg2 is needed to reconstruct the correlation function, assuming smaller beam sizes of future surveys (e.g., the Large Millimeter Telescope's 6'' beam size). At present, robust measures of the clustering strength of bright SMGs appear to be below the reach of most observations.
We present high angular resolution (~0".75) MIR spectra of the powerful radio galaxy, Cygnus A (Cyg A), obtained with the Subaru telescope. The overall shape of the spectra agree with previous high ...angular resolution MIR observations, as well as previous Spitzer spectra. Our spectra, both on and off nucleus, show a deep silicate absorption feature. The absorption feature can be modeled with a blackbody obscured by cold dust or a clumpy toms. The deep silicate feature is best fit by a simple model of a screened blackbody, suggesting that foreground absorption plays a significant, if not dominant, role in shaping the spectrum of Cyg A. This foreground absorption prevents a clear view of the central engine and surrounding toms, making it difficult to quantify the extent the torus attributes to the obscuration of the central engine, but does not eliminate the need for a torus in Cyg A.
ABSTRACT The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg2 of the ...SMC with 1 noise levels of 5-12 mJy beam−1, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 m, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500 m). The 1.1 mm objects show dust temperatures of 17-45 K and gas masses of 4 × 103-3 × 105 M , assuming single-temperature thermal emission from the cold dust with an emissivity index, β, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 m and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.
ABSTRACT
We present stacking analyses on our ALMA deep 1.1 mm imaging in the Subaru/
XMM-Newton
Deep Survey Field using 1.6 and 3.6
μ
m selected galaxies in the CANDELS WFC3 catalog. We detect a ...stacked flux of ∼0.03–0.05 mJy, corresponding to
and a star formation rate (SFR) of
yr
−1
at
z
= 2. We find that galaxies that are brighter in the rest-frame near-infrared tend to also be brighter at 1.1 mm, and galaxies fainter than
do not produce detectable 1.1 mm emission. This suggests a correlation between stellar mass and SFR, but outliers to this correlation are also observed, suggesting strongly boosted star formation or extremely large extinction. We also find tendencies that redder galaxies and galaxies at higher redshifts are brighter at 1.1 mm. Our field contains
H
α
emitters and a bright single-dish source. However, we do not find evidence of bias in our results caused by the bright source. By combining the fluxes of sources detected by ALMA and fluxes of faint sources detected with stacking, we recover a 1.1 mm surface brightness of up to 20.3 ± 1.2 Jy deg
−2
, comparable to the extragalactic background light measured by
COBE
. Based on the fractions of optically faint sources in our and previous ALMA studies and the
COBE
measurements, we find that approximately half of the cosmic star formation may be obscured by dust and missed by deep optical surveys. Much deeper and wider ALMA imaging is therefore needed to better constrain the obscured cosmic star formation history.
Synergies among the IAU Offices Govender, Kevin; Cheung, Sze-Leung; Aretxaga, Itziar ...
Proceedings of the International Astronomical Union,
08/2018, Letnik:
14, Številka:
A30
Journal Article
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