Massive clusters of galaxies have been found that date from as early as 3.9 billion years (3.9 Gyr; z = 1.62) after the Big Bang, containing stars that formed at even earlier epochs. Cosmological ...simulations using the current cold dark matter model predict that these systems should descend from 'protoclusters'-early overdensities of massive galaxies that merge hierarchically to form a cluster. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies that can be observed as luminous quasars and starbursts. Observational evidence for this picture, however, is sparse because high-redshift protoclusters are rare and difficult to observe. Here we report a protocluster region that dates from 1 Gyr (z = 5.3) after the Big Bang. This cluster of massive galaxies extends over more than 13 megaparsecs and contains a luminous quasar as well as a system rich in molecular gas. These massive galaxies place a lower limit of more than 4 × 10(11) solar masses of dark and luminous matter in this region, consistent with that expected from cosmological simulations for the earliest galaxy clusters.
High-resolution Airborne Wide-band Camera (HAWC
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) is the facility far-infrared imager and polarimeter for SOFIA, NASA’s Stratospheric Observatory for Infrared Astronomy. It is designed to cover the ...portion of the infrared spectrum that is completely inaccessible to ground-based observatories and which is essential for studies of astronomical sources with temperatures between tens and hundreds of degrees Kelvin. Its ability to make polarimetric measurements of aligned dust grains provides a unique new capability for studying interstellar magnetic fields. HAWC
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began commissioning flights in April 2016 and was accepted as a facility instrument in early 2018. In this paper, we describe the instrument, its operational procedures, and its performance on the observatory.
Spectroscopic, cold, space-based mid-to-far-infrared (FIR) missions, such as the Origins Space Telescope, will require large (tens of kilopixels), ultra-sensitive FIR detector arrays with sufficient ...dynamic range and high-density multiplexing schemes for the readout, in order to optimize the scientific return while staying within a realistic cost range. Issues like power consumption of multiplexers and their readout are significantly more important for space missions than they are for ground-based or suborbital applications. In terms of the detectors and their configuration into large arrays, significant development efforts are needed even for both of the most mature candidate superconducting detector technologies, namely transition edge sensors and (microwave) kinetic inductance detectors. Here we explore both practical and fundamental limits for those technologies in order to lay out a realistic path forward for both technologies. We conclude that beyond the need to enhance the detector sensitivities and pixel numbers by about an order of magnitude over currently existing devices, improved concepts for larger dynamic range and multiplexing density will be needed in order to optimize the scientific return of future cold FIR space missions. Background-limited, very high spectral resolution instruments will require photon-counting detectors.
We present deep continuum observations using the GISMO camera at a wavelength of 2 mm centered on the Hubble Deep Field in the GOODS-N field. These are the first deep field observations ever obtained ...at this wavelength. The 1sigma sensitivity in the innermost ~4' of the 7' diameter map is ~135 mu Jy beam super(-1), a factor of three higher in flux/beam sensitivity than the deepest available SCUBA 850 mu m observations, and almost a factor of four higher in flux/beam sensitivity than the combined MAMBO/AzTEC 1.2 mm observations of this region. Our source extraction algorithm identifies 12 sources directly, and another 3 through correlation with known sources at 1.2 mm and 850 mu m. Five of the directly detected GISMO sources have counterparts in the MAMBO/AzTEC catalog, and four of those also have SCUBA counterparts. HDF850.1, one of the first blank-field detected submillimeter galaxies, is now detected at 2 mm. The median redshift of all sources with counterparts of known redshifts is z = 2.91 + or - 0.94. Statistically, the detections are most likely real for five of the seven 2 mm sources without shorter wavelength counterparts, while the probability for none of them being real is negligible.
We present super(12)CO(J= 110) observations of the high-redshift quasi-stellar objects (QSOs) BR 1202-0725 (z =4.69), PSS J2322+1944 (z = 4.12), and APM 08279+5255 (z = 3.91)using the NRAO Green Bank ...Telescope (GBT) and the MPIfR Effelsberg 100 m telescope. We detect, for the first time, the CO ground-level transition in BR 1202-0725. For PSS J2322+1944 and APM 08279+5255, our observations result in line fluxes that are consistent with previous NRAO Very Large Array (VLA) observations, but they reveal the full line profiles. We report a typical lensing-corrected velocity-integrated intrinsic super(12)CO(J = 110 line luminosity of L super('CO)=5 x 10 super(10) K km s super(-1) pc super(2) and a typical total H sub(2) mass of M(H sub(2)) = 4 x 10 super(10) M sub( )for the sources in our sample. The CO/FIR luminosity ratios of these high-z sources follow the same trend as seen for low-z galaxies, leading to a combined solution of log L sub(FIR) = (1.39 c 0.05) log L sub(CO) -1.76. It has previously been suggested that the molecular gas reservoirs in some quasar host galaxies may exhibit luminous, extended super(12)CO(J = 110) components that are not observed in the higher J CO transitions. Using the line profiles and the total intensities of our observations and large velocity gradient (LVG) models based on previous results for higher JCO transitions, we derive that emission from all CO transitions is described well by a single gas component in which all molecular gas is concentrated in a compact nuclear region. Thus, our observations and models show no indication of aluminous extended, low surface brightness molecular gas component in any of the high-redshift QSOs in our sample. If such extended components exist, their contribution to the overall luminosity is limited to at most 30%.
Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as ...observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PEGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of ~200 Myr, with an SFR of ~500 M yr--1. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.
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