A deep ALMA image of the Hubble Ultra Deep Field Dunlop, J. S; McLure, R. J; Biggs, A. D ...
Monthly notices of the Royal Astronomical Society,
04/2017, Letnik:
466, Številka:
1
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Abstract
We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ≃4.5 arcmin2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera ...3/IR on HST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching σ1.3 ≃ 35 μJy, at a resolution of ≃0.7 arcsec. From an initial list of ≃50 > 3.5σ peaks, a rigorous analysis confirms 16 sources with S
1.3 > 120 μJy. All of these have secure galaxy counterparts with robust redshifts (〈z〉 = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses (M
*) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M
* ≥ 2 × 1010 M⊙, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S
1.3 ≃ 10 μJy. We find strong evidence for a steep star-forming ‘main sequence’ at z ≃ 2, with SFR ∝M
* and a mean specific SFR ≃ 2.2 Gyr−1. Moreover, we find that ≃85 per cent of total star formation at z ≃ 2 is enshrouded in dust, with ≃65 per cent of all star formation at this epoch occurring in high-mass galaxies (M
* > 2 × 1010 M⊙), for which the average obscured:unobscured SF ratio is ≃200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ≃ 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ≃ 4.
We present a 1.1 mm wavelength imaging survey covering 0.3 deg2 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 z≈ 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 deg2 area which has a uniform sensitivity of ∼1.3 mJy beam−1. 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 × 1012L⊙ and star formation rates >1100 M⊙ yr−1. 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.
CCAT-prime is a new 6 m crossed Dragone telescope designed to characterize the cosmic microwave background (CMB) polarization and foregrounds, measure the Sunyaev–Zel’dovich effects of galaxy ...clusters, map the CII emission intensity from the epoch of reionization (EoR), and monitor accretion luminosity over multiyear timescales of hundreds of protostars in the Milky Way. CCAT-prime will make observations from a 5600-m-altitude site on Cerro Chajnantor in the Atacama Desert of northern Chile. The novel optical design of the telescope combined with high-surface-accuracy (
<
10
μ
m) mirrors and the exceptional atmospheric conditions of the site will enable sensitive broadband, polarimetric, and spectroscopic surveys at sub-millimeter to millimeter wavelengths. Prime-Cam, the first light instrument for CCAT-prime, consists of a 1.8-m-diameter cryostat that can house seven individual instrument modules. Each instrument module, optimized for a specific science goal, will use state-of-the-art kinetic inductance detector (KID) arrays operated at
∼
100
mK and Fabry–Perot interferometers (FPI) for the EoR science. Prime-Cam will be commissioned with staged deployments to populate the seven instrument modules. The full instrument will consist of 60,000 polarimetric KIDs at a combination of 220/280/350/410 GHz, 31,000 KIDS at 250/360 GHz coupled with FPIs, and 21,000 polarimetric KIDs at 850 GHz. Prime-Cam is currently being built, and the CCAT-prime telescope is designed and under construction by Vertex Antennentechnik GmbH to achieve first light in 2021. CCAT-prime is also a potential telescope platform for the future CMB Stage IV observations.
SUMMARY
Fossil corals are commonly used to reconstruct Last Interglacial (∼125 ka, LIG) sea level. Sea level reconstructions assume the water depth at which the coral lived, called the ‘relative ...water depth’. However, relative water depth varies in time and space due to coral reef growth in response to relative sea level (RSL) changes. RSL changes can also erode coral reefs, exposing older reef surfaces with different relative water depths. We use a simplified numerical model of coral evolution to investigate how sea level history systematically influences the preservation of corals in the Bahamas and western Australia, regions which house >100 LIG coral fossils. We construct global ice histories spanning the uncertainty of LIG global mean sea level (GMSL) and predict RSL with a glacial isostatic adjustment model. We then simulate coral evolution since 132 ka. We show that preserved elevations and relative water depths of modelled LIG corals are sensitive to the magnitude, timing and number of GMSL highstand(s). In our simulations, the influence of coral growth and erosion (i.e. the ‘growth effect’) can have an impact on RSL reconstructions that is comparable to glacial isostatic adjustment. Thus, without explicitly accounting for the growth effect, additional uncertainty is introduced into sea level reconstructions. Our results suggest the growth effect is most pronounced in western Australia due to Holocene erosion, but also plays a role in the Bahamas, where LIG RSL rose rapidly due to the collapsing peripheral bulge associated with Laurentide Ice Sheet retreat. Despite the coral model's simplicity, our study highlights the utility of process-based RSL reconstructions.
Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, ...Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies-imaged in intensity and polarization at few arcminute-scale resolution-will enable precision cosmological constraints and also awide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the AdvancedACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the AdvancedACTPol cryogenic detector arrays.
The AzTEC mm-wavelength camera Wilson, G. W.; Austermann, J. E.; Perera, T. A. ...
Monthly notices of the Royal Astronomical Society,
20/May , Letnik:
386, Številka:
2
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AzTEC is a mm-wavelength bolometric camera utilizing 144 silicon nitride micromesh detectors. Here, we describe the AzTEC instrument architecture and its use as an astronomical instrument. We report ...on several performance metrics measured during a three-month observing campaign at the James Clerk Maxwell Telescope and conclude with our plans for AzTEC as a facility instrument on the Large Millimetre Telescope.
Estimates of peak global mean sea level (GMSL) during the Last Interglacial (LIG, ∼129-116 ka) based on geological sea level high-stand markers require a correction for the contaminating influence of ...glacial isostatic adjustment (GIA). This correction is obtained by calculating the viscoelastic response of the Earth to changes in the ice and ocean load prior to and following the LIG. While ice retreat over the last deglaciation is relatively well constrained, changes in ice cover prior to the LIG are more uncertain. We investigate the sensitivity of numerical predictions of GIA during the LIG to variations in the geometry of pre-LIG ice cover and the timing of the deglaciation into the LIG, with a particular focus on Marine Isotope Stage (MIS) 6 (∼190-130 ka). We demonstrate that reconstructing the pre-LIG ice history by replicating the last glacial cycle back in time, rather than using ice volume approximations based on oxygen isotope records, can introduce errors in LIG high-stand predictions of ∼5 m at sites on the peripheral bulge of major ice complexes, and up to ∼2 m at far-field sites. We also demonstrate that predictions of LIG sea level are more sensitive to the geographic distribution of ice cover during MIS 6 than previously recognized. Adopting simulations which vary the relative size of Late Pleistocene ice cover over North America and Eurasia can yield a change in predicted high-stand elevations of ∼5 m in both the near and far field of northern hemisphere ice sheets. This far-field sensitivity arises, in part, from the reorientation of Earth's rotation axis during MIS 6, which in turn drives sea-level changes with a distinct geographic signature. In future work we will apply the insights gained here to re-evaluate the observed geographic variability in geological high-stand markers of LIG age and estimates of GMSL based upon them.
•The ice history prior to the Last Interglacial (LIG) is uncertain.•This uncertainty changes glacial isostatic adjustment during the LIG by multiple meters.•Near-field sites are mainly affected due to differences in the peripheral bulge height.•Far-field sites are mainly affected due to true polar wander.
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