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Register a new userCO J=1-0 spectroscopy of four submillimeter galaxies with the Zpectrometer on the Green Bank Telescope
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A.I. Harris
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We report detections of three z ~ 2.5 submillimeter-selected galaxies (SMGs; SMM J14011+0252, SMM J14009+0252, SMM J04431+0210) in the lowest rotational transition of the carbon monoxide molecule (CO J = 1-0) and one nondetection (SMM J04433+0210). For the three galaxies we detected, we find a line-integrated brightness temperature ratio of the J = 3-2 and 1-0 lines of 0.68 +/- 0.08; the 1-0 line is stronger than predicted by the frequent assumption of equal brightnesses in the two lines and by most single-component models. The observed ratio suggests that mass estimates for SMGs based on J = 3-2 observations and J = 1-0 column density or mass conversion factors are low by a factor of 1.5. Comparison of the 1-0 line intensities with intensities of higher-J transitions indicates that single-component models for the interstellar media in SMGs are incomplete. The small dispersion in the ratio, along with published detections of CO lines with J_upper > 3 in most of the sources, indicates that the emission is from multi-component interstellar media with physical structures common to many classes of galaxies. This result tends to rule out the lowest scaling factors between CO luminosity and molecular gas mass, and further increases molecular mass estimates calibrated against observations of galaxies in the local universe. We also describe and demonstrate a statistically sound method for finding weak lines in broadband spectra that will find application in searches for molecular lines from sources at unknown redshifts.
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We report measurements of the carbon monoxide ground state rotational transition (12C16O J = 1--0) with the Zpectrometer ultra-wideband spectrometer on the 100-m diameter Green Bank Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100um. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO redshift distribution of the 350um-selected galaxies is strikingly similar to the optical redshifts of 850um-selected submillimeter galaxies (SMGs) in 2.1 < z < 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies and statistically significant nondetections hint at warmer or molecule-poor DSFGs with redshifts difficult determine from from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications mu from spectroscopic data alone, yielding mu ~ 3--20. Corrected for magnification, most galaxy luminosities are consistent with an ultra-luminous infrared galaxy (ULIRG) classification, but three are candidate hyper-LIRGs with luminosities greater than 10^13 L_sun.
We report deep K-band (18-27GHz) observations with the 100-m Green Bank Telescope of HCN(1-0) line emission towards the two submillimeter-selected galaxies (SMGs) SMMJ02399-0136 (z=2.81) and SMMJ16359+6612 (z=2.52). For both sources we have obtained spectra with channel-to-channel rms noise of <=0.5mJy, resulting in velocity-integrated line fluxes better than < 0.1 Jy km/s, although we do not detect either source. Such sensitive observations -- aided by gravitational lensing of the sources -- permit us to put upper limits of L_HCN(1-0) < 2x10^10 K km/s pc^2 on the intrinsic HCN(1-0) line luminosities of the two SMGs. The far-infrared (FIR) luminosities for all three SMGs with sensitive HCN(1-0) observations to date are found to be consistent with the tight FIR-HCN luminosity correlation observed in Galactic molecular clouds, quiescent spirals and (ultra) luminous infrared galaxies in the local Universe. Thus, the observed HCN luminosities remain in accordance with what is expected from the universal star formation efficiency per dense molecular gas mass implied by the aforementioned correlation, and more sensitive observations with todays large aperture radio telescopes hold the promise of detecting HCN(1-0) emission in similar objects in the distant Universe.
This document summarizes the results of a community-based discussion of the potential science impact of the Mayall+BigBOSS highly multiplexed multi-object spectroscopic capability. The KPNO Mayall 4m telescope equipped with the DOE- and internationally-funded BigBOSS spectrograph offers one of the most cost-efficient ways of accomplishing many of the pressing scientific goals identified for this decade by the New Worlds, New Horizons report. The BigBOSS Key Project will place unprecedented constraints on cosmological parameters related to the expansion history of the universe. With the addition of an open (publicly funded) community access component, the scientific impact of BigBOSS can be extended to many important astrophysical questions related to the origin and evolution of galaxies, stars, and the IGM. Massive spectroscopy is the critical missing ingredient in numerous ongoing and planned ground- and space-based surveys, and BigBOSS is unique in its ability to provide this to the US community. BigBOSS data from community-led projects will play a vital role in the education and training of students and in maintaining US leadership in these fields of astrophysics. We urge the NSF-AST division to support community science with the BigBOSS multi-object spectrograph through the period of the BigBOSS survey in order to ensure public access to the extraordinary spectroscopic capability.
We present the joint analysis of Neutral Hydrogen (HI) Intensity Mapping observations with three galaxy samples: the Luminous Red Galaxy (LRG) and Emission Line Galaxy (ELG) samples from the eBOSS survey, and the WiggleZ Dark Energy Survey sample. The HI intensity maps are Green Bank Telescope observations of the redshifted 21cm emission on 100deg2 covering the redshift range $0.6<z<1.0$. We process the data by separating and removing the foregrounds with FastICA, and construct a transfer function to correct for the effects of foreground removal on the HI signal. We cross-correlate the cleaned HI data with the galaxy samples and study the overall amplitude as well as the scale-dependence of the power spectrum. We also qualitatively compare our findings with the predictions by a semi-analytic galaxy evolution simulation. The cross-correlations constrain the quantity $Omega_{{HI}} b_{{HI}} r_{{HI},{opt}}$ at an effective scale $k_{eff}$, where $Omega_{HI}$ is the HI density fraction, $b_{HI}$ is the HI bias, and $r_{{HI},{opt}}$ the galaxy-hydrogen correlation coefficient, which is dependent on the HI content of the optical galaxy sample. At $k_{eff}=0.31 , h/{Mpc}$ we find $Omega_{{HI}} b_{{HI}} r_{{HI},{Wig}} = [0.58 pm 0.09 , {(stat) pm 0.05 , {(sys)}}] times 10^{-3}$ for GBT-WiggleZ, $Omega_{{HI}} b_{{HI}} r_{{HI,{ELG}}} = [0.40 pm 0.09 , {(stat) pm 0.04 , {(sys)}}] times 10^{-3}$ for GBT-ELG, and $Omega_{{HI}} b_{{HI}} r_{{HI},{LRG}} = [0.35 pm 0.08 , {(stat) pm 0.03 , {(sys)}}] times 10^{-3}$ for GBT-LRG, at $zsimeq 0.8$. We also report results at $k_{eff}=0.24 , h/{Mpc}$ and $k_{eff}=0.48 , h/{Mpc}$. With little information on HI parameters beyond our local Universe, these are amongst the most precise constraints on neutral hydrogen density fluctuations in an underexplored redshift range.
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