Showing papers by "Fabian Walter published in 2016"
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TL;DR: Pan-STARRS1 has carried out a set of distinct synoptic imaging sky surveys including the 3ππ$ Steradian Survey and the Medium Deep Survey in 5 bands as mentioned in this paper.
Abstract: Pan-STARRS1 has carried out a set of distinct synoptic imaging sky surveys including the $3\pi$ Steradian Survey and the Medium Deep Survey in 5 bands ($grizy_{P1}$). The mean 5$\sigma$ point source limiting sensitivities in the stacked 3$\pi$ Steradian Survey in $grizy_{P1}$ are (23.3, 23.2, 23.1, 22.3, 21.4) respectively. The upper bound on the systematic uncertainty in the photometric calibration across the sky is 7-12 millimag depending on the bandpass. The systematic uncertainty of the astrometric calibration using the Gaia frame comes from a comparison of the results with Gaia: the standard deviation of the mean and median residuals ($ \Delta ra, \Delta dec $) are (2.3, 1.7) milliarcsec, and (3.1, 4.8) milliarcsec respectively. The Pan-STARRS system and the design of the PS1 surveys are described and an overview of the resulting image and catalog data products and their basic characteristics are described together with a summary of important results. The images, reduced data products, and derived data products from the Pan-STARRS1 surveys are available to the community from the Mikulski Archive for Space Telescopes (MAST) at STScI.
1,257 citations
Leiden University1, Diego Portales University2, Max Planck Society3, California Institute of Technology4, Swinburne University of Technology5, Australian National University6, Millennium Institute7, Pontifical Catholic University of Chile8, Space Science Institute9, University of Bonn10, University of Cambridge11, Dalhousie University12, Paris Diderot University13, University of Edinburgh14, European Southern Observatory15, Cornell University16, Durham University17, Yale University18, University of Sussex19
TL;DR: In this paper, the authors make use of deep 1.2 mm continuum observations (12.7 μJy beam−1 rms) of a 1 arcmin² region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2−10 (to ∼2-3 M⊙ yr−1 at 1σ over the entire range).
Abstract: We make use of deep 1.2 mm continuum observations (12.7 μJy beam−1 rms) of a 1 arcmin² region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2–10 (to ∼2–3 M⊙ yr−1 at 1σ over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies, extrapolating the Meurer z ∼ 0 IRX–β relation to z > 2 (assuming dust temperature Td ∼ 35 K). However, only six tentative detections are found at z >~ 2 in ASPECS, with just three at >3σ. Subdividing our z = 2–10 galaxy samples according to stellar mass, UV luminosity, and UV-continuum slope and stacking the results, we find a significant detection only in the most massive (>109.75 Me) subsample, with an infrared excess (IRX = LIR/LUV) consistent with previous z ∼ 2 results. However, the infrared excess we measure from our large selection of sub-L∗ ( ~ 2 galaxies. We find that the evolution of the IRX–stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (µ +1 z 0.32 ( ) ) such that Td ∼ 44–50 K at z 4, current results are suggestive of little evolution in this relationship to z ∼ 6. We use these results to revisit recent estimates of the z > 3 star formation rate density.
308 citations
Leiden University1, Durham University2, University of Edinburgh3, Max Planck Society4, University of Bonn5, European Southern Observatory6, Pennsylvania State University7, Dalhousie University8, McGill University9, Spanish National Research Council10, University of Vienna11, University College London12, Science and Technology Facilities Council13, Chalmers University of Technology14
TL;DR: In this article, high-resolution (0 ''.6) 870 mu m Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (LIR similar to 4 x 10(12) L-circle dot) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South was presented.
Abstract: We present high-resolution (0 ''.6) 870 mu m Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (LIR similar to 4 x 10(12) L-circle dot) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z similar to 2.5 galaxies on similar to 1.3 kpc scales. The emission has a median effective radius of R-e = 0 ''.24 +/- 0 ''.02, corresponding to a typical physical size of R-e= 1.8 +/- 0.2 kpc. We derive a median Sersic index of n = 0.9 +/- 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0 ''.12. (similar to 1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope H-160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z similar to 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive (M* similar to 1-2 x 10(11) M-circle dot) early-type galaxies observed locally.
271 citations
TL;DR: In this article, high-resolution (0.16$"$) 870um Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (L_IR ~ 4 x 10^12 L_sun) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South.
Abstract: We present high-resolution (0.16$"$) 870um Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (L_IR ~ 4 x 10^12 L_sun) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z~2.5 galaxies on ~1.3 kpc scales. The emission has a median effective radius of $R_e=0.24" \pm 0.02"$, corresponding to a typical physical size of $R_{e}=1.8\pm$0.2 kpc. We derive a median S\'ersic index of $n=0.9\pm0.2$, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0.12$"$ (~1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate S/N interferometric data. We compare our maps to comparable-resolution HST H$_{160}$-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the $z\sim0$ descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive (M_* ~ 1-2 x 10^11 M_sun) early-type galaxies observed locally.
242 citations
National Radio Astronomy Observatory1, Max Planck Society2, California Institute of Technology3, Diego Portales University4, University of Cambridge5, Leiden University6, Australian National University7, Swinburne University of Technology8, Paris Diderot University9, European Southern Observatory10, University of Edinburgh11, Cornell University12, Durham University13, Millennium Institute14, Andrés Bello National University15, University of Lyon16, Space Science Institute17, Pontifical Catholic University of Chile18, University of Michigan19, University of Bonn20, Dalhousie University21, Spanish National Research Council22, University of Arizona23, Valparaiso University24, Aix-Marseille University25, Yale University26, University of Sussex27, NASA Headquarters28
TL;DR: In this article, the authors present the rationale for and the observational description of ASPECS: the ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available.
Abstract: We present the rationale for and the observational description of ASPECS: the ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z > 0.5) galaxies. The ~1' region covered within the UDF was chosen to overlap with the deepest available imaging from the Hubble Space Telescope. Our ALMA observations consist of full frequency scans in band 3 (84–115 GHz) and band 6 (212–272 GHz) at approximately uniform line sensitivity (L’_(CO) ~ 2 × 10^9 K km s^(−1) pc^2), and continuum noise levels of 3.8 μJy beam^(−1) and 12.7 μJy beam^(−1), respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [C II] emission line is also covered at redshifts 6.0 < z < 8.0. We present a customized algorithm to identify line candidates in the molecular line scans and quantify our ability to recover artificial sources from our data. Based on whether multiple CO lines are detected, and whether optical spectroscopic redshifts as well as optical counterparts exist, we constrain the most likely line identification. We report 10 (11) CO line candidates in the 3 mm (1 mm) band, and our statistical analysis shows that <4 of these (in each band) are likely spurious. Less than one-third of the total CO flux in the low-J CO line candidates are from sources that are not associated with an optical/NIR counterpart. We also present continuum maps of both the band 3 and band 6 observations. The data presented here form the basis of a number of dedicated studies that are presented in subsequent papers.
231 citations
Leiden University1, Diego Portales University2, Max Planck Society3, California Institute of Technology4, Australian National University5, Swinburne University of Technology6, Space Science Institute7, Millennium Institute8, Pontifical Catholic University of Chile9, University of Bonn10, University of Cambridge11, Dalhousie University12, Paris Diderot University13, University of Edinburgh14, European Southern Observatory15, Cornell University16, Durham University17, Yale University18, University of Sussex19
TL;DR: In this article, the authors make use of deep 1.2mm-continuum observations (12.7microJy/beam RMS) of a 1 arcmin^2 region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z=2-10 (to ~2-3 Msol/yr at 1sigma over the entire range).
Abstract: We make use of deep 1.2mm-continuum observations (12.7microJy/beam RMS) of a 1 arcmin^2 region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z=2-10 (to ~2-3 Msol/yr at 1sigma over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies extrapolating the Meurer z~0 IRX-beta relation to z>~2 (assuming T_d~35 K). However, only 6 tentative detections are found at z>~2 in ASPECS, with just three at >3sigma. Subdividing z=2-10 galaxies according to stellar mass, UV luminosity, and UV-continuum slope and stacking the results, we only find a significant detection in the most massive (>10^9.75 Msol) subsample, with an infrared excess (IRX=L_{IR}/L_{UV}) consistent with previous z~2 results. However, the infrared excess we measure from our large selection of sub-L* ( ~2 galaxies. We furthermore find that the evolution of the IRX-stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (as (1+z)^0.32) such that T_d~44-50 K at z>=4, current results are suggestive of little evolution in this relationship to z~6. We use these results to revisit recent estimates of the z>~3 SFR density. One less obvious implication is in interpreting the high Halpha EWs seen in z~5 galaxies: our results imply that star-forming galaxies produce Lyman-continuum photons at twice the efficiency (per unit UV luminosity) as implied in conventional models. Star-forming galaxies can then reionize the Universe, even if the escape fraction is <10%.
186 citations
Diego Portales University1, Max Planck Society2, California Institute of Technology3, Swinburne University of Technology4, Millennium Institute5, Space Science Institute6, Pontifical Catholic University of Chile7, University of Cambridge8, Paris Diderot University9, University of Edinburgh10, European Southern Observatory11, Cornell University12, Durham University13, Andrés Bello National University14, University of Michigan15, University of Bonn16, University of Lyon17, Leiden University18, Valparaiso University19, Aix-Marseille University20, NASA Headquarters21
TL;DR: In this paper, the authors presented an analysis of a deep (1σ = 13 μJy) cosmological 1.2 mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field.
Abstract: We present an analysis of a deep (1σ = 13 μJy) cosmological 1.2 mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin^2 covered by ASPECS we detect nine sources at >3.5σ significance at 1.2 mm. Our ALMA-selected sample has a median redshift of z = 1.6 ± 0.4, with only one galaxy detected at z > 2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cutoff and similar frequencies. Most galaxies have specific star formation rates (SFRs) similar to that of main-sequence galaxies at the same epoch, and we find median values of stellar mass and SFRs of 4.0 x 10^(10)M⊙ and ~40 M⊙ yr^(-1), respectively. Using the dust emission as a tracer for the interstellar medium (ISM) mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from ~0.1 to 1.0. As noted by previous studies, these values are lower than those using CO-based ISM estimates by a factor of ~2. The 1 mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover 55% ± 4% of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover 80% ± 7% of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at z ~ 1-2, with stellar masses of (1–3) × 10^(10) M⊙. For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm.
159 citations
TL;DR: In this paper, the authors presented an analysis of a deep (1$\sigma$=13 $\mu$Jy) cosmological 1.2mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field.
Abstract: We present an analysis of a deep (1$\sigma$=13 $\mu$Jy) cosmological 1.2-mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin$^2$ covered by ASPECS we detect nine sources at $>3.5\sigma$ significance at 1.2-mm. Our ALMA--selected sample has a median redshift of $z=1.6\pm0.4$, with only one galaxy detected at z$>$2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cut-off and similar frequencies. Most galaxies have specific star formation rates similar to that of main sequence galaxies at the same epoch, and we find median values of stellar mass and star formation rates of $4.0\times10^{10}\ M_\odot$ and $\sim40~M_\odot$ yr$^{-1}$, respectively. Using the dust emission as a tracer for the ISM mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from $\sim$0.1 to 1.0. As noted by previous studies, these values are lower than using CO--based ISM estimates by a factor $\sim$2. The 1\,mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover $55\pm4\%$ of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover $80\pm7\%$ of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at $z\sim1-2$, with stellar masses of (1-3)$\times$10$^{10}$ M$_\odot$. For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm.
140 citations
Max Planck Society1, University of Leeds2, Curtin University3, National Radio Astronomy Observatory4, University of Calgary5, University of Massachusetts Amherst6, California Institute of Technology7, West Virginia University8, Liverpool John Moores University9, Heidelberg University10, University of Kent11, University of Cologne12, Australian National University13, University of Manchester14, Indian Institute of Science15
TL;DR: In this paper, the authors used the Karl G. Jansky Very Large Array (VLA) in the C-array configuration and a large program to observe the HI 21 cm line, four OH lines, nineteen Hn alpha radio recombination lines as well as the continuum emission from 1 to 2 GHz in full polarization over a large part of the first Galactic quadrant.
Abstract: Context. The past decade has witnessed a large number of Galactic plane surveys at angular resolutions below 20 `'. However, no comparable high-resolution survey exists at long radio wavelengths around 21 cm in line and continuum emission. Aims. We remedy this situation by studying the northern Galactic plane at similar to 20 `' resolution in emission of atomic, molecular, and ionized gas. Methods. Employing the Karl G. Jansky Very Large Array (VLA) in the C-array configuration and a large program, we observe the HI 21 cm line, four OH lines, nineteen Hn alpha radio recombination lines as well as the continuum emission from 1 to 2 GHz in full polarization over a large part of the first Galactic quadrant. Results. Covering Galactic longitudes from 14.5 to 67.4 deg and latitudes between +/- 1.25 deg, we image all of these lines and the continuum at similar to 20 `' resolution. These data allow us to study the various components of the interstellar medium (ISM): from the atomic phase, traced by the HI line, to the molecular phase, observed by the OH transitions, to the ionized medium, revealed by the cm continuum and the Hn alpha radio recombination lines. Furthermore, the polarized continuum emission enables magnetic field studies. In this overview paper, we discuss the survey outline and present the first data release as well as early results from the different datasets. We now release the first half of the survey; the second half will follow later after the ongoing data processing has been completed. The data in fits format (continuum images and line data cubes) can be accessed through the project web-page. Conclusions. The HI/OH/Recombination line survey of the Milky Way (THOR) opens a new window to the different parts of the ISM. It enables detailed studies of molecular cloud formation, conversion of atomic to molecular gas, and feedback from HII regions as well as the magnetic field in the Milky Way. It is highly complementary to other surveys of our Galaxy, and comparing the different datasets will allow us to address many open questions.
140 citations
Max Planck Society1, California Institute of Technology2, National Radio Astronomy Observatory3, Diego Portales University4, University of Cambridge5, Leiden University6, Swinburne University of Technology7, Australian National University8, Paris Diderot University9, Cornell University10, Durham University11, University of Lyon12, Pontifical Catholic University of Chile13, Millennium Institute14, Space Science Institute15, University of Michigan16, University of Bonn17, Dalhousie University18, Spanish National Research Council19, European Southern Observatory20, University of Edinburgh21, University of Sussex22
TL;DR: In this paper, the authors studied the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ~1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands.
Abstract: We study the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ~1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities L_(IR) > 10^(11) L_☉, i.e., a detection in CO emission was expected. Out of these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the CO-detected galaxies in the UDF tend to reside on the low- L_(IR) envelope of the scatter in the L_(IR)-L^'_(CO)relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of ~1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio M_(H2)/M *) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor ~2–5× smaller than those based on CO. When we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.
130 citations
TL;DR: In this paper, the authors studied the molecular gas properties of high-z$ galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets a ∼1$ arcmin$^2$ region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3mm and 1mm bands.
Abstract: We study the molecular gas properties of high-$z$ galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets a $\sim1$ arcmin$^2$ region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3mm and 1mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities $L_{\rm{}IR}>10^{11}$ L$_\odot$, i.e. a detection in CO emission was expected. Out these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than typically found in starburst/SMG/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in context of previous molecular gas observations at high redshift (star-formation law, gas depletion times, gas fractions): The CO-detected galaxies in the UDF tend to reside on the low-$L_{\rm{}IR}$ envelope of the scatter in the $L_{\rm{}IR}-L'_{\rm{}CO}$ relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of $\sim$ 1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio ($M_{\rm{}H2}$/$M_*$) is consistent with earlier measurements of main sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor $\sim$2-5$\times$ smaller than those based on CO. Accounting for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.
Max Planck Society1, California Institute of Technology2, National Radio Astronomy Observatory3, Diego Portales University4, University of Cambridge5, Leiden University6, Swinburne University of Technology7, Australian National University8, Paris Diderot University9, University of Edinburgh10, European Southern Observatory11, Cornell University12, Durham University13, Andrés Bello National University14, Millennium Institute15, Pontifical Catholic University of Chile16, Space Science Institute17, University of Michigan18, University of Bonn19, Dalhousie University20, Autonomous University of Madrid21, University of Arizona22, Valparaiso University23, Aix-Marseille University24, Yale University25, University of Sussex26
TL;DR: FONDECYT [1140099, 1151408], National Science Foundation [AST-1614213] and Concicyt grant Basal-CATA [PFB-06/2007].
Abstract: FONDECYT [1140099, 1151408]; National Science Foundation [AST-1614213]; Concicyt grant Basal-CATA [PFB-06/2007]; Concicyt grant Anilo [ACT1417]; FONDECYT Regular [1141218]; Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]; STFC [ST/L00075X/1]; Collaborative Research Council 956, sub-project A1 - Deutsche Forschungsgemeinschaft (DFG); German ARC; ERC grant COSMIC-DAWN; ERC grant DUSTYGAL; ERC grant COSMICISM
Diego Portales University1, Max Planck Society2, California Institute of Technology3, National Radio Astronomy Observatory4, University of California, Santa Cruz5, Leiden University6, Yale University7, University of Cambridge8, Space Science Institute9, Pontifical Catholic University of Chile10, Swinburne University of Technology11, Australian National University12, Paris Diderot University13, European Southern Observatory14, University of Edinburgh15, Cornell University16, Durham University17, Andrés Bello National University18, Millennium Institute19, Claude Bernard University Lyon 120, University of Michigan21, University of Bonn22, Atacama Large Millimeter Submillimeter Array23, Valparaiso University24, Ludwig Maximilian University of Munich25
TL;DR: In this article, a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF).
Abstract: We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212–272 GHz, encompass approximately the range of 6 4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S_(1.2 mm) = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M⊙ yr^(-1). We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L_([C II]) versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.
TL;DR: In this paper, the authors present a search for [CII] line and dust continuum emission from optical dropout galaxies at $z>6$ using ASPECS, their ALMA Spectroscopic Survey in the Hubble Ultra-Deep Field (UDF).
Abstract: We present a search for [CII] line and dust continuum emission from optical dropout galaxies at $z>6$ using ASPECS, our ALMA Spectroscopic Survey in the Hubble Ultra-Deep Field (UDF). Our observations, which cover the frequency range $212-272$ GHz, encompass approximately the range $6 $4.5 $\sigma$, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60\% of our candidates are expected to be spurious. For one of our blindly selected [CII] line candidates, we tentatively detect the CO(6-5) line in our parallel 3-mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [CII] candidates results in a tentative detection with $S_{1.2mm}=14\pm5\mu$Jy. This implies a dust-obscured star formation rate (SFR) of $(3\pm1)$ M$_\odot$ yr$^{-1}$. We find that the two highest--SFR objects have candidate [CII] lines with luminosities that are consistent with the low-redshift $L_{\rm [CII]}$ vs. SFR relation. The other candidates have significantly higher [CII] luminosities than expected from their UV--based SFR. At the current sensitivity it is unclear whether the majority of these sources are intrinsically bright [CII] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [CII] emitters at $6
University of Toledo1, Max Planck Society2, Ohio State University3, Princeton University4, University of Cambridge5, University of California, San Diego6, California Institute of Technology7, University of Maryland, College Park8, University of Antofagasta9, Leiden University10, Delft University of Technology11, Reed College12, University of Wyoming13, European Southern Observatory14, Australian National University15, INAF16
TL;DR: In this paper, the authors present [C II] 158 μm measurements from over 15,000 resolved regions within 54 nearby galaxies of the Kingfish program to investigate the line-cooling deficit in galaxies with different luminosities.
Abstract: We present [C II] 158 μm measurements from over 15,000 resolved regions within 54 nearby galaxies of the Kingfish program to investigate the so-called [C II] "line-cooling deficit" long known to occur in galaxies with different luminosities. The [C II]/TIR ratio ranges from above 1% to below 0.1% in the sample, with a mean value of 0.48 ± 0.21%. We find that the surface density of 24 μm emission dominates this trend, with [C II]/TIR dropping as νl_ν (24 µm) increases. Deviations from this overall decline are correlated with changes in the gas-phase metal abundance, with higher metallicity associated with deeper deficits at a fixed surface brightness. We supplement the local sample with resolved [C II] measurements from nearby luminous infrared galaxies and high-redshift sources from z = 1.8–6.4, and find that star formation rate density drives a continuous trend of deepening [C II] deficit across six orders of magnitude in Σ_(SFR). The tightness of this correlation suggests that an approximate Σ_(SFR) can be estimated directly from global measurements of [C II]/TIR, and a relation is provided to do so. Several low-luminosity active galactic nucleus (AGN) hosts in the sample show additional and significant central suppression of [C II]/TIR, but these deficit enhancements occur not in those AGNs with the highest X-ray luminosities, but instead those with the highest central starlight intensities. Taken together, these results demonstrate that the [C II] line-cooling line deficit in galaxies likely arises from local physical phenomena in interstellar gas.
TL;DR: The emergence of cosmological structures of the Chinese Academy of Sciences (XDB09000000) as discussed by the authors has been proposed as a priority research program for the Chinese National Key Basic Research Program (NKBP).
Abstract: IRAM Plateau de Bure Interferometer [S14CY]; VLA [14B151, 15A494]; JCMT/SCUBA-2 [M15BI055]; INSU/CNRS (France); MPG (Germany); IGN (Spain); Chinese Academy of Sciences [XDB09000000]; Science and Technology Facilities Council of the United Kingdom; National Science Foundation of China (NSFC) [11373008, 11533001]; Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences [XDB09000000]; National Key Basic Research Program of China [2014CB845700]; Ministry of Science and Technology of China [2016YFA0400703]; Thousand Youth Talents Program of China; NSFC grants [11443002, 11473004]; NSF Grants [AST 11-07682, 15-15115]
TL;DR: In this article, the authors analyzed the velocity dispersions of individual H I and CO profiles in a number of nearby galaxies from the high-resolution HERACLES CO and THINGS H I surveys.
Abstract: We analyze the velocity dispersions of individual H I and CO profiles in a number of nearby galaxies from the high-resolution HERACLES CO and THINGS H I surveys. Focusing on regions with bright CO emission, we find a CO dispersion value sigma(Co) = 7.3 +/- 1.7 km s(-1). The corresponding H I dispersion sigma(H I) = 11.7 +/- 2.3 km s(-1), yielding a mean dispersion ratio sigma(HI)/sigma(CO) = 1.4 +/- 0.2, independent of radius. We find that the CO velocity dispersion increases toward lower peak fluxes. This is consistent with previous work where we showed that when using spectra averaged ("stacked") over large areas, larger values for the CO dispersion are found, and a lower ratio sigma(HI)/sigma(CO) = 1.0 +/- 0.2. The stacking method is more sensitive to low-level diffuse emission, whereas individual profiles trace narrow-line, GMC-dominated, bright emission. These results provide further evidence that disk galaxies contain not only a thin, low velocity dispersion, high density CO disk that is dominated by GMCs, but also a fainter, higher dispersion, diffuse disk component.
Max Planck Society1, California Institute of Technology2, National Radio Astronomy Observatory3, Diego Portales University4, University of Cambridge5, Leiden University6, Australian National University7, Swinburne University of Technology8, Paris Diderot University9, University of Edinburgh10, European Southern Observatory11, Cornell University12, Durham University13, Andrés Bello National University14, Millennium Institute15, Pontifical Catholic University of Chile16, Space Science Institute17, University of Michigan18, University of Bonn19, Dalhousie University20, Autonomous University of Madrid21, University of Arizona22, Valparaiso University23, Aix-Marseille University24, Yale University25, University of Sussex26
TL;DR: In this paper, the authors used the ALMA Spectroscopic Survey (ASPECS) in the Hubble Ultra Deep Field (UDF) to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to 4.5.
Abstract: In this paper we use ASPECS, the ALMA Spectroscopic Survey in the {\em Hubble} Ultra Deep Field (UDF) in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to $z\sim 4.5$. This study is based on galaxies that have been solely selected through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted `knee' of the CO luminosity function (around $5\times10^{9}$ K km/s pc$^2$). We find clear evidence of an evolution in the CO luminosity function with respect to $z\sim 0$, with more CO luminous galaxies present at $z\sim 2$. The observed galaxies at $z\sim 2$ also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a factor 3-10 drop from $z \sim 2$ to $z \sim 0$ (with significant error bars), and possibly a decline at $z>3$. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation ($z\sim2$).
Max Planck Society1, University of Maryland, College Park2, University of Toledo3, Princeton University4, Heidelberg University5, Ohio State University6, University of Cambridge7, University of Massachusetts Amherst8, Reed College9, California Institute of Technology10, Leiden University11, University of California, San Diego12, European Southern Observatory13, Delft University of Technology14, Australian National University15, University of Oxford16, Spanish National Research Council17
TL;DR: In this article, the authors investigated the relationship between the [N ii] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities.
Abstract: The [N ii] 122 and 205 μm transitions are powerful tracers of the ionized gas in the interstellar medium By combining data from 21 galaxies selected from the Herschel KINGFISH and Beyond the Peak surveys, we have compiled 141 spatially resolved regions with a typical size of ~1 kpc, with observations of both [N ii] far-infrared lines We measure [N ii] 122/205 line ratios in the ~06–6 range, which corresponds to electron gas densities of n_e ~ 1–300 cm^(−3), with a median value of n_e = 30 cm^(−3) Variations in the electron density within individual galaxies can be as high as a factor of ~50, frequently with strong radial gradients We find that n_e increases as a function of infrared color, dust-weighted mean starlight intensity, and star-formation rate (SFR) surface density (Σ_(SFR)) As the intensity of the [N ii] transitions is related to the ionizing photon flux, we investigate their reliability as tracers of the SFR We derive relations between the [N ii] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities The scatter in the correlation between [N ii] surface brightness and Σ_(SFR) can be understood as a property of the n_e distribution For regions with n_e close to or higher than the [N ii] line critical densities, the low-density limit [N ii]-based SFR calibration systematically underestimates the SFR because the [N ii] emission is collisionally quenched Finally, we investigate the relation between [N ii] emission, SFR, and n_e by comparing our observations to predictions from the MAPPINGS-III code
TL;DR: In this paper, the authors present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array for 14 z similar to 2 galaxies with existing CO(3-2) measurements, including 11 galaxies that contain active galactic nuclei and three submillimeter galaxies (SMGs).
Abstract: We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array for 14 z similar to 2 galaxies with existing CO(3-2) measurements, including 11 galaxies that. contain active galactic nuclei (AGNs) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 z similar to 2 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, to. measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. With our expanded sample of CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically significant difference in the mean line ratio between SMGs and AGN host galaxies as can be found in the literature; we instead find r(3,1) = 1.03. 0.50 for AGN host galaxies and r(3,1) = 0.78. 0.27 for SMGs (or r(3,1) = 0.90 +/- 0.40 for both populations combined). We also do not measure a statistically significant difference between the distributions of the line ratios for these populations at the p = 0.05 level, although this result is less robust. We find no excitation dependence on the index or offset of the integrated Schmidt-Kennicutt relation for the two CO lines, and we. obtain indices consistent with N = 1 for the various subpopulations. However, including low-z "normal" galaxies increases our best-fit Schmidt-Kennicutt index to N similar to 1.2. While we do not reproduce correlations between the CO line width and luminosity, we do reproduce correlations between CO excitation and star-formation efficiency.
TL;DR: In this paper, the authors derived relations between the [NII] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities.
Abstract: The [NII] 122 and 205 \mu m transitions are powerful tracers of the ionized gas in the interstellar medium. By combining data from 21 galaxies selected from the Herschel KINGFISH and Beyond the Peak surveys, we have compiled 141 spatially resolved regions with a typical size of ~1 kiloparsec, with observations of both [NII] far-infrared lines. We measure [NII] 122/205 line ratios in the ~0.6-6 range, which corresponds to electron gas densities $n_e$~1-300 cm$^{-3}$, with a median value of $n_e$=30 cm$^{-3}$. Variations in the electron density within individual galaxies can be as a high as a factor of ~50, frequently with strong radial gradients. We find that $n_e$ increases as a function of infrared color, dust-weighted mean starlight intensity, and star formation rate surface density ($\Sigma_{SFR}$). As the intensity of the [NII] transitions is related to the ionizing photon flux, we investigate their reliability as tracers of the star formation rate (SFR). We derive relations between the [NII] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities. The scatter in the correlation between [NII] surface brightness and $\Sigma_{SFR}$ can be understood as a property of the $n_e$ distribution. For regions with $n_e$ close to or higher than the [NII] line critical densities, the low-density limit [NII]-based SFR calibration systematically underestimates the SFR since [NII] emission is collisionally quenched. Finally, we investigate the relation between [NII] emission, SFR, and $n_e$ by comparing our observations to predictions from the MAPPINGS-III code.
California Institute of Technology1, Max Planck Society2, National Radio Astronomy Observatory3, Stony Brook University4, University of Hawaii5, Yukawa Institute for Theoretical Physics6, Harvard University7, NASA Headquarters8, European Southern Observatory9, Ohio State University10, University of California, Santa Cruz11, Massachusetts Institute of Technology12, Leiden University13
TL;DR: In this article, the internal gas distribution and kinematics of both galactic nuclei are well-resolved for the first time, yielding the emissivity distributions, the rotation curves and velocity dispersions.
Abstract: We present 90 mas (37 pc) resolution ALMA imaging of Arp 220 in the CO (1-0) line and continuum at $\lambda = 2.6$ mm. The internal gas distribution and kinematics of both galactic nuclei are well-resolved for the first time. In the West nucleus, the major gas and dust emission extends out to 0.2\arcsec radius (74 pc); the central resolution element shows a strong peak in the dust emission but a factor 3 dip in the CO line emission. In this nucleus, the dust is apparently optically thick ($\tau_{\rm 2.6mm} \sim1$) at $\lambda = 2.6$ mm with a dust brightness temperature $\sim147$ K. The column of ISM at this nucleus is $\rm N_{H2} \geq 2\times10^{26}$ cm$^{-2}$, corresponding to $\sim$900 gr cm$^{-2}$. The East nucleus is more elongated with radial extent 0.3\arcsec or $\sim111$ pc. The derived kinematics of the nuclear disks provide a good fit to the line profiles, yielding the emissivity distributions, the rotation curves and velocity dispersions. In the West nucleus, there is evidence of a central Keplerian component requiring a central mass of $8\times10^8$ \msun. The intrinsic widths of the emission lines are $\Delta \rm v (FWHM)$ = 250 (West) and 120 (East) \kms. Given the very short dissipation timescales for turbulence ($\lesssim10^5$ yrs), we suggest that the line widths may be due to semi-coherent motions within the nuclear disks. The symmetry of the nuclear disk structures is impressive -- implying the merger timescale is significantly longer than the rotation period of the disks.
TL;DR: In this paper, the authors present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array (VLA) for 14 z~2 galaxies with existing CO(3-2) measurements, including 11 galaxies which contain active galactic nuclei (AGN) and three submillimeter galaxies (SMGs).
Abstract: We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array (VLA) for 14 z~2 galaxies with existing CO(3-2) measurements, including 11 galaxies which contain active galactic nuclei (AGN) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 z~2 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. With our expanded sample of CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically significant difference in the mean line ratio between SMGs and AGN host galaxies as found in the literature, instead finding r_3,1=1.03+/-0.50 for AGN host galaxies and r_3,1=0.78+/-0.27 for SMGs (or r_3,1=0.90+/-0.40 for both populations combined). We also do not measure a statistically significant difference between the distributions of the line ratios for these populations at the p=0.05 level, although this result is less robust. We find no excitation dependence on the index or offset of the integrated Schmidt-Kennicutt relation for the two CO lines, and obtain indices consistent with N=1 for the various sub-populations. However, including low-z "normal" galaxies increases our best-fit Schmidt-Kennicutt index to N~1.2. While we do not reproduce correlations between the CO line width and luminosity, we do reproduce correlations between CO excitation and star formation efficiency.
Max Planck Society1, University of Toledo2, Ohio State University3, Princeton University4, University of Cambridge5, University of California, San Diego6, California Institute of Technology7, University of Maryland, College Park8, University of Antofagasta9, Delft University of Technology10, Leiden University11, Reed College12, University of Wyoming13, European Southern Observatory14, Australian National University15, INAF16
TL;DR: In this paper, the authors present [CII] 158um measurements from over 15,000 resolved regions within 54 nearby galaxies of the KINGFISH program to investigate the so-called "line cooling deficit" long known to occur in galaxies with different luminosities.
Abstract: We present [CII] 158um measurements from over 15,000 resolved regions within 54 nearby galaxies of the KINGFISH program to investigate the so-called [CII] "line cooling deficit" long known to occur in galaxies with different luminosities. The [CII]/TIR ratio ranges from above 1% to below 0.1% in the sample, with a mean value of 0.48+-0.21%. We find that the surface density of 24um emission dominates this trend, with [CII]/TIR dropping as nuInu{24um} increases. Deviations from this overall decline are correlated with changes in the gas phase metal abundance, with higher metallicity associated with deeper deficits at a fixed surface brightness. We supplement the local sample with resolved [CII] measurements from nearby luminous infrared galaxies and high redshift sources from z=1.8-6.4, and find that star formation rate density drives a continuous trend of deepening [CII] deficit across six orders of magnitude in SFRD. The tightness of this correlation suggests that an approximate star formation rate density can be estimated directly from global measurements of [CII]/TIR, and a relation is provided to do so. Several low-luminosity AGN hosts in the sample show additional and significant central suppression of [CII]/TIR, but these deficit enhancements occur not in those AGN with the highest X-ray luminosities, but instead those with the highest central starlight intensities. Taken together, these results demonstrate that the [CII] cooling line deficit in galaxies likely arises from local physical phenomena in interstellar gas.
TL;DR: In this article, the authors present ALMA observations of the inner 1' (1.2 kpc) of the Circinus galaxy, the nearest Seyfert galaxy, and constrain the mass of the outflowing molecular gas to be 1.5e5 -5.1e6 solar masses, yielding a molecular outflow rate of 0.35-12.3 solar masses per year.
Abstract: We present ALMA observations of the inner 1' (1.2 kpc) of the Circinus galaxy, the nearest Seyfert. We target CO (1-0) in the region associated with a well-known multiphase outflow driven by the central active galactic nucleus (AGN). While the geometry of Circinus and its outflow make disentangling the latter difficult, we see indications of outflowing molecular gas at velocities consistent with the ionized outflow. We constrain the mass of the outflowing molecular gas to be 1.5e5 -5.1e6 solar masses, yielding a molecular outflow rate of 0.35-12.3 solar masses per year. The values within this range are comparable to the star formation rate in Circinus, indicating that the outflow indeed regulates star formation to some degree. The molecular outflow in Circinus is considerably lower in mass and energetics than previously-studied AGN-driven outflows, especially given its high ratio of AGN luminosity to bolometric luminosity. The molecular outflow in Circinus is, however, consistent with some trends put forth in Cicone et al. (2014), including a linear relation between kinetic power and AGN luminosity, as well as its momentum rate vs. bolometric luminosity (although the latter places Circinus among the starburst galaxies in that sample). We detect additional molecular species including CN and C17O.
Max Planck Society1, California Institute of Technology2, National Radio Astronomy Observatory3, Diego Portales University4, University of Cambridge5, Leiden University6, Australian National University7, Swinburne University of Technology8, Paris Diderot University9, European Southern Observatory10, University of Edinburgh11, Cornell University12, Durham University13, Millennium Institute14, Andrés Bello National University15, University of Lyon16, Space Science Institute17, Pontifical Catholic University of Chile18, University of Michigan19, University of Bonn20, Dalhousie University21, Spanish National Research Council22, University of Arizona23, Valparaiso University24, Aix-Marseille University25, Yale University26, University of Sussex27, NASA Headquarters28
TL;DR: In this paper, the authors present the rationale for and the observational description of ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available.
Abstract: We present the rationale for and the observational description of ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z$>$0.5) galaxies. The $\sim$1$'$ region covered within the UDF was chosen to overlap with the deepest available imaging from HST. Our ALMA observations consist of full frequency scans in band 3 (84-115 GHz) and band 6 (212-272 GHz) at approximately uniform line sensitivity ($L'_{\rm CO}\sim$2$\times$10$^{9}$ K km/s pc$^2$), and continuum noise levels of 3.8 $\mu$Jy beam$^{-1}$ and 12.7 $\mu$Jy beam$^{-1}$, respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [CII] emission line is also covered at redshifts $6.0
TL;DR: In this paper, the authors proposed a method to improve the performance of the National Aeronautics and Space Administration (NNX08AR22G), National Science Foundation (NSF), and the Ministry of Science and Technology (MoST) of Taiwan through grant National Science Council (NSC) and MoST of Taiwan.
Abstract: National Aeronautics and Space Administration [NNX08AR22G]; National Science Foundation [AST-1238877]; Ministry of Science and Technology (MoST) of Taiwan through grant National Science Council (NSC) [103-2112-M-007-002-MY3, 105-2112-M-007-003-MY3]; MoST of Taiwan [NSC 100-2112-M-001-001-MY3, 104-2112-M-001-034-, 105-2112-M-001-024-]
TL;DR: In this paper, the authors present direct estimates of the mean sky brightness temperature in observing bands around 99GHz and 242GHz due to line emission from distant galaxies using ALMA (ASPECS) survey.
Abstract: We present direct estimates of the mean sky brightness temperature in observing bands around 99GHz and 242GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for spectral line emission from high redshift galaxies using ALMA (the ’ASPECS’ survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242GHz band, the emission could be a combination of higher order CO lines, and possibly [CII] 158μm line emission from very high redshift galaxies (z ∼ 6 to 7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early Universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99GHZ band is: TB = 0.94 ± 0.09μK. In the 242GHz band, the mean brightness is: TB = 0.55 ± 0.033μK. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey.
TL;DR: In this paper, the authors compare the kinematics of the molecular (CO from HERACLES) and atomic (H i from THINGS) gas distributions to determine the extent to which CO may be used to probe the dynamics in the inner part of galaxies.
Abstract: We present CO velocity fields and rotation curves for a sample of nearby galaxies, based on data from HERACLES. We combine our data with THINGS, SINGS, and KINGFISH results to provide a comprehensive sample of mass models of disk galaxies inclusive of molecular gas. We compare the kinematics of the molecular (CO from HERACLES) and atomic (H i from THINGS) gas distributions to determine the extent to which CO may be used to probe the dynamics in the inner part of galaxies. In general, we find good agreement between the CO and H i kinematics, with small differences in the inner part of some galaxies. We add the contribution of the molecular gas to the mass models in our galaxies by using two different conversion factors αCO to convert CO luminosity to molecular gas mass surface density—the constant Milky Way value and the radially varying profiles determined in recent work based on THINGS, HERACLES, and KINGFISH data. We study the relative effect that the addition of the molecular gas has on the halo rotation curves for Navarro-Frenk-White and the observationally motivated pseudo-isothermal halos. The contribution of the molecular gas varies for galaxies in our sample—for those galaxies where there is a substantial molecular gas content, using different values of αCO can result in significant differences to the relative contribution of the molecular gas and hence the shape of the dark matter halo rotation curves in the central regions of galaxies.
TL;DR: In this article, the authors present a survey for intervening MgII absorption towards 100 quasars with emission redshifts between 3.55$ and 7.08$ using infrared spectra from Magellan/FIRE, and confirm that the incidence rate of $W_r>0.3 A$ Mg II absorption per comoving path length does not evolve measurably between $z=0.25$ and $z
Abstract: We present final statistics from a survey for intervening MgII absorption towards 100 quasars with emission redshifts between $z=3.55$ and $z=7.08$. Using infrared spectra from Magellan/FIRE, we detect 279 cosmological MgII absorbers, and confirm that the incidence rate of $W_r>0.3 A$ MgII absorption per comoving path length does not evolve measurably between $z=0.25$ and $z=7$. This is consistent with our detection of seven new MgII systems at $z>6$, a redshift range that was not covered in prior searches. Restricting to relatively strong MgII systems ($W_r>1$A), there is significant evidence for redshift evolution. These systems roughly double in number density between $z=0$ and $z=2$-$3$, but decline by an order of magnitude from this peak by $z\sim 6$. This evolution mirrors that of the global star formation rate density, which could reflect a connection between star formation feedback and strong MgII absorbers. We compared our results to the Illustris cosmological simulation at $z=2$-$4$ by assigning absorption to catalogued dark-matter halos and by direct extraction of spectra from the simulation volume. To reproduce our results using the halo catalogs, we require circumgalactic (CGM) MgII envelopes within halos of progressively smaller mass at earlier times. This occurs naturally if we define the lower integration cutoff using SFR rather than mass. MgII profiles calculated directly from the Illustris volume yield far too few strong absorbers. We argue that this arises from unresolved phase space structure of CGM gas, particularly from turbulent velocities on sub-mesh scales. The presence of CGM MgII at $z>6$-- just $\sim 250$ Myr after the reionization redshift implied by Planck--suggests that enrichment of intra-halo gas may have begun before the presumed host galaxies' stellar populations were mature and dynamically relaxed. [abridged]