SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) [Website] is a proposed all-sky spectroscopic survey satellite designed to address all three science goals in NASA's Astrophysics Division: probe the origin and destiny of our Universe; explore whether planets around other stars could harbor life; and explore the origin and evolution of galaxies. SPHEREx will scan a series of Linear Variable Filters systematically across the entire sky. The SPHEREx data set will contain R=40 spectra fir 0.75< λ <4.1µm and R=150 spectra for 4.1< λ <4.8µm for every 6.2 arcsecond pixel over the entire-sky. In this paper, we detail the extra-galactic and cosmological studies SPHEREx will enable and present detailed systematic effect evaluations. We also outline the Ice and Galaxy Evolution Investigations. I. SPHEREX MISSION OVERVIEWSPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer; PI: J. Bock) is a proposed all-sky survey satellite designed to address all three science goals in NASA's Astrophysics Division: probe the origin and destiny of our Universe; explore whether planets around other stars could harbor life; and explore the origin and evolution of galaxies. All of these exciting science themes are addressed by a single survey, with a single instrument, providing the first near-infrared spectroscopy of the complete sky. In this paper, we will focus on the cosmological science enabled by SPHEREx and outline the Galactic Ices and the Epoch of Reionization (EOR) scientific investigations.SPHEREx will probe the origin of the Universe by constraining the physics of inflation, the superluminal expansion of the Universe that took place some 10 −32 s after the Big Bang. SPHEREx will study its imprints in the threedimensional large-scale distribution of matter by measuring galaxy redshifts over a large cosmological volume at low redshifts, complementing high-redshift surveys optimized to constrain dark energy.SPHEREx will investigate the origin of water and biogenic molecules in all phases of planetary system formation -from molecular clouds to young stellar systems with protoplanetary disks -by measuring absorption spectra to determine the abundance and composition of ices toward > 2 × 10 4 Galactic targets. Interstellar ices are the likely source for water and organic molecules, the chemical basis of life on Earth, and knowledge of their abundance is key to understanding the formation of young planetary systems as well as the prospects for life on other planets.SPHEREx will chart the origin and history of galaxy formation through a deep survey mapping large-scale structure. This technique measures the total light produced by all galaxy populations, complementing studies based on deep galaxy counts, to trace the history of galactic light production from the present day to the first galaxies that ended the cosmic dark ages.SPHEREx will be the first all-sky near-infrared spectral survey, creating a legacy archive of spectra (0.75 ≤ λ ≤...

Trends observed in galaxies, such as the Gao & Solomon relation, suggest a linear relationship between the star formation rate and the mass of dense gas available for star formation. Validation of such trends requires the establishment of reliable methods to trace the dense gas in galaxies. One frequent assumption is that the HCN (J = 1-0) transition is unambiguously associated with gas at H 2 densities 10 4 cm −3 . If so, the mass of gas at densities 10 4 cm −3 could be inferred from the luminosity of this emission line, L HCN (1-0) . Here we use observations of the Orion A molecular cloud to show that the HCN (J = 1-0) line traces much lower densities ∼10 3 cm −3 in cold sections of this molecular cloud, corresponding to visual extinctions A V ≈ 6 mag. We also find that cold and dense gas in a cloud like Orion produces too little HCN emission to explain L HCN (1-0) in star forming galaxies, suggesting that galaxies might contain a hitherto unknown source of HCN emission. In our sample of molecules observed at frequencies near 100 GHz (also including 12 CO, 13 CO, C 18 O, CN, and CCH), N 2 H + is the only species clearly associated with relatively dense gas.

We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2 − 37 µm spectral region, provide detailed maps of the 8 lowest pure rotational lines of molecular hydrogen and of the [SI] 25.25 µm and [FeII] 26.0 µm fine structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heated by a non-dissociative shock, allow the energetics of the outflows to be elucidated. Within the regions mapped towards these 5 outflow sources, total H 2 luminosities ranging from 0.02 to 0.75 L ⊙ were inferred for the sum of the 8 lowest pure rotational transitions. By contrast, the much weaker [FeII] 26.0 µm fine structure transition traces faster, dissociative shocks; here, only a small fraction of the fast shock luminosity emerges as line radiation that can be detected with Spitzer/IRS. Chen et al. (2008) using both the Australian Telescope Compact Array and Spitzer, reveal masses of 2.12 and 0.05 M ⊙ , hydrogen (H+2H 2 ) densities of 2.6 and 2.2×10 7 cm −3 , and hydrogen column densities of 9.4 and 2.6×10 23 cm −2 , respectively. Fits to the spectral energy distribution of IRS 1 and IRS 2 based on these more recent data imply bolometric luminosities Recent observations of the circumstellar envelope around IRS 1 and IRS 2 by

We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 1_{10}-1_{01} transition of ortho-water at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, Rho Oph A, NGC 2024, CRL 2591, W3, W3(OH), Mon R2, and W33, and was not detected in TMC-1, L134N, and B335. We also present a small map of the water emission in S140. Observations of the H_2^{18}O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-water relative to H_2 in the giant molecular cloud cores was found to vary between 6x10^{-10} and 1x10^{-8}. Five of the cloud cores in our sample have previous water detections; however, in all cases the emission is thought to arise from hot cores with small angular extents. The water abundance estimated for the hot core gas is at least 100 times larger than in the gas probed by SWAS. The most stringent upper limit on the ortho-water abundance in dark clouds is provided in TMC-1, where the 3-sigma upper limit on the ortho-water fractional abundance is 7x10^{-8}.Comment: 5 pages, 3 Postscript figures, uses aastex.cls, emulateapj5.sty (included), and apjfonts.sty (included

No abstract

No abstract

No abstract

SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, is a proposed NASA MIDEX mission selected for Phase A study pointing to a downselect in early CY2019, leading to launch in CY2023. SPHEREx would carry out the first all-sky spectral survey at wavelengths between 0.75 and 2.42 µm [with spectral resolution R=41], 2.42 and 3.82 µm [with R=35], 3.82 and 4.42 µm [with R=110], and 4.42 and 5.00 µm [with R=130]. At the end of its two-year mission, SPHEREx would obtain 0.75-to-5µm spectra of every 6.2×6.2 arcsec pixel on the sky, with a 5-sigma sensitivity AB>19 per spectral/spatial resolution element. SPHEREx would obtain spectra of every sources in the 2MASS PSC (1.2µm, 1.6µm, 2.2µm) catalog to at least (40 σ, 60 σ, 150 σ) per spectral channel, and spectra with S/N ≥3 per frequency element of the faintest sources detected by WISE. More details concerning SPHEREx are available at http://spherex.caltech.edu. The SPHEREx team has proposed three specific science investigations to be carried out with this unique data set: cosmic inflation, interstellar and circumstellar ices, and the extra-galactic background light.Though these three scientific issues are undoubtedly compelling, they are far from exhausting the scientific output of SPHEREx. Indeed, as Table 1 shows, SPHEREx would create a unique all-sky spectral database including spectra of very large numbers of astronomical and solar system targets, including both extended and diffuse sources. These spectra would enable a wide variety of scientific investigations, and the SPHEREx team is dedicated to making the SPHEREx data available to the scientific community to facilitate these investigations, which we refer to as Legacy Science. To that end, we have sponsored two workshops for the general scientific community to identify the most interesting Legacy Science themes and to ensure that the SPHEREx data products are responsive to their needs. In February of 2016, some 50 scientists from all scientific fields met in Pasadena to develop these themes and to understand their implications for the SPHEREx mission. The results of this initial workshop are reported in Doré et al., 2016. Among other things, discussions at the 2016 workshop highlighted many synergies between SPHEREx Legacy Science and other contemporaneous astronomical missions, facilities, and databases. Consequently, in January 2018 we convened a second workshop at the Center for Astrophysics in Cambridge to focus specifically on these synergies. This white paper, which contains substantial contributions from the participants, presents some of the highlights of the 2018 SPHEREx workshop. 1