Hydrogen Sulfide and Ammonia Receptor Concentrations in a Community of Multiple Swine Emission Sources: Preliminary Study

A Mobile Ambient Laboratory (MAL) was placed at a residence in a community with two swine-barn emission sites and one land application area to observe real-time atmospheric stability, ammonia (NH3) and hydrogen sulfide (H2S) concentrations surrounding and within the residence during a 12-week period. Significant differences in NH3 and H2S concentrations with atmospheric stability were found. For NH3, significantly higher concentrations were measured inside the residence compared to ambient NH3 concentrations, and these levels were not correlated with outside ambient conditions. For H2S, significantly higher levels were measured outside the residence for downwind occurrences during low wind (=0.45 m s-1) and low solar (\u3c10 W m-2) conditions indicative of very stable atmospheres. The concentrations and durations of NH3 and H2S measured in the ambient air surrounding the residence were far below recommended Minimum Risk Levels published by the U.S. Department of Health and Human Service\u27s, Agency for Toxic Substances and Disease Registry, for the protection of sensitive populations

Source and Receptor Ammonia and Hydrogen Sulfide Concentrations in Communities with and without Swine Emission Sources: Follow-Up Study

Research was conducted from May 2004 through September 2005 to investigate the concentration of hydrogen sulfide (H2S) at the perimeter of nine swine operations across the state of Iowa and the ammonia (NH3) and H2S concentrations near and inside residences located in the community of swine operations and in one area of the state not associated with animal agriculture. The nine sources monitored ranged from sites that housed approximately 1,800 to 4,000 finishing pigs. The results indicated that at the perimeter of all nine sources monitored, the overall average H2S concentration ranged from 1.9±2.7 ppb to 26.3±32.3 ppb (mean±S.D.). Downwind samples, or samples collected during calm periods, resulted in average H2S concentrations that ranged from 7.4±6.9 ppb to 45.8±31.8 ppb. In both cases, the maximum H2S concentration was recorded at a finishing site where an earthen basin and a concrete formed below-grade basin existed in close proximity to the livestock housing. Measurements of H2S and NH3 were also conducted at five residences, four of which were located near the swine operation sites for perimeter H2S levels, with one located in an urban setting far removed from animal agriculture. The overall daily average NH3 concentration measured inside the homes ranged from 28.6±12.8 ppb to 94.7±28.1 ppb. The overall daily average NH3 concentration measured in the ambient air outside the homes ranged from 11.7±5.3 ppb to 55.1±20.6 ppb. The NH3 concentration inside the homes were significantly higher than in the ambient air outside of the homes (p\u3c0.01). H2S concentration inside the homes ranged from 0.7±0.2 ppb to 2.5±1.5 ppb. Hydrogen sulfide concentration in the ambient air outside the home ranged from 0.4±0.2 ppb to2.4±2.4 ppb. For the residence monitored in an urban setting far removed from animal agriculture, the overall average H2S concentration outside the home was 0.4±0.2 ppb with the inside home averaging 0.7±0.2 ppb. The highest average inside home concentration for NH3 and H2S was 94.7±28.1 ppb and 2.5±1.5 ppb, respectively, both from a residence where the occupants smoked. The next highest inside home NH3 concentration was 85.7±15.3 ppb. For this residence the occupants did not smoke but felines were kept inside. The results from the residence ambient air monitoring indicate that the concentration and duration for either NH3 or H2S fell well below the Minimum Risk Levels (MRL) as defined by the Agency for Toxic Substances and Disease Registry (ATSDR, 2008)

Dependence of Galaxy Quenching on Halo Mass and Distance from its Centre

We study the dependence of star-formation quenching on galaxy mass and environment, in the SDSS (z~0.1) and the AEGIS (z~1). It is crucial that we define quenching by low star-formation rate rather than by red colour, given that one third of the red galaxies are star forming. We address stellar mass M*, halo mass Mh, density over the nearest N neighbours deltaN, and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites quenching also depends on D. We present the M*-Mh relation for centrals at z~1. At z~1, the dependence of quenching on M* at fixed Mh is somewhat more pronounced than at z~0, but the quenched fraction is low (10%) and the haloes are less massive. For satellites, M*-dependent quenching is noticeable at high D, suggesting a quenching dependence on sub-halo mass for recently captured satellites. At small D, where satellites likely fell in more than a few Gyr ago, quenching strongly depends on Mh, and not on M*. The Mh-dependence of quenching is consistent with theoretical wisdom where virial shock heating in massive haloes shuts down accretion and triggers ram-pressure stripping, causing quenching. The interpretation of deltaN is complicated by the fact that it depends on the number of observed group members compared to N, motivating the use of D as a better measure of local environment.Comment: 23 pages, 13 figures, accepted by MNRA

Absence of Evidence Is Not Evidence of Absence: The Color-Density Relation at Fixed Stellar Mass Persists to z ~ 1

We use data drawn from the DEEP2 Galaxy Redshift Survey to investigate the relationship between local galaxy density, stellar mass, and rest-frame galaxy color. At z ~ 0.9, we find that the shape of the stellar mass function at the high-mass (log (M*/Msun) > 10.1) end depends on the local environment, with high-density regions favoring more massive systems. Accounting for this stellar mass-environment relation (i.e., working at fixed stellar mass), we find a significant color-density relation for galaxies with 10.6 < log(M*/Msun) < 11.1 and 0.75 < z < 0.95. This result is shown to be robust to variations in the sample selection and to extend to even lower masses (down to log(M*/Msun) ~ 10.4). We conclude by discussing our results in comparison to recent works in the literature, which report no significant correlation between galaxy properties and environment at fixed stellar mass for the same redshift and stellar mass domain. The non-detection of environmental dependence found in other data sets is largely attributable to their smaller samples size and lower sampling density, as well as systematic effects such as inaccurate redshifts and biased analysis techniques. Ultimately, our results based on DEEP2 data illustrate that the evolutionary state of a galaxy at z ~ 1 is not exclusively determined by the stellar mass of the galaxy. Instead, we show that local environment appears to play a distinct role in the transformation of galaxy properties at z > 1.Comment: 10 pages, 5 Figures; Accepted for publication in MNRA

P-MaNGA : full spectral fitting and stellar population maps from prototype observations

MC acknowledges support from a Royal Society University Research Fellowship.MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) is a 6-yearSDSS-IV survey that will obtain resolved spectroscopy from 3600 Å to10300 Å for a representative sample of over 10,000 nearby galaxies.In this paper, we derive spatially resolved stellar population properties and radial gradients by performing full spectral fitting of observed galaxy spectra from P-MaNGA, a prototype of the MaNGA instrument. These data include spectra for eighteen galaxies, covering a large range of morphological type. We derive age, metallicity, dust and stellar mass maps, and their radial gradients, using high spectral-resolution stellar population models, and assess the impact of varying the stellar library input to the models. We introduce a method to determine dust extinction which is able to give smooth stellar mass maps even in cases of high and spatially non-uniform dust attenuation.With the spectral fitting we produce detailed maps of stellar population properties which allow us to identify galactic features among this diverse sample such as spiral structure, smooth radial profiles with little azimuthal structure in spheroidal galaxies, and spatially distinct galaxy sub-components. In agreement with the literature, we find the gradients for galaxies identified as early-type to be on average flat in age, and negative (- 0.15 dex / Re ) in metallicity,whereas the gradients for late-type galaxies are on average negative in age (- 0.39 dex / Re ) and flat in metallicity. We demonstrate howdifferent levels of data quality change the precision with which radialgradients can be measured. We show how this analysis, extended to thelarge numbers of MaNGA galaxies, will have the potential to shed lighton galaxy structure and evolution.PostprintPeer reviewe

SDSS-IV MaNGA: the spectroscopic discovery of strongly lensed galaxies

We present a catalogue of 38 spectroscopically detected strong galaxy–galaxy gravitational lens candidates identified in the Sloan Digital Sky Survey IV (SDSS-IV). We were able to simulate narrow-band images for eight of them demonstrating evidence of multiple images. Two of our systems are compound lens candidates, each with two background source-planes. One of these compound systems shows clear lensing features in the narrow-band image. Our sample is based on 2812 galaxies observed by the Mapping Nearby Galaxies at APO (MaNGA) integral field unit (IFU). This Spectroscopic Identification of Lensing Objects (SILO) survey extends the methodology of the Sloan Lens ACS Survey (SLACS) and BOSS Emission-Line Survey (BELLS) to lower redshift and multiple IFU spectra. We searched ∼1.5 million spectra, of which 3065 contained multiple high signal-to-noise ratio background emission-lines or a resolved [O ii] doublet, that are included in this catalogue. Upon manual inspection, we discovered regions with multiple spectra containing background emission-lines at the same redshift, providing evidence of a common source-plane geometry which was not possible in previous SLACS and BELLS discovery programs. We estimate more than half of our candidates have an Einstein radius ≳ 1.7 arcsec, which is significantly greater than seen in SLACS and BELLS. These larger Einstein radii produce more extended images of the background galaxy increasing the probability that a background emission-line will enter one of the IFU spectroscopic fibres, making detection more likely

X-ray selected AGN in groups at redshifts z~1

We explore the role of the group environment in the evolution of AGN at the redshift interval 0.7<z<1.4, by combining deep Chandra observations with extensive optical spectroscopy from the All-wavelength Extended Groth strip International Survey (AEGIS). The sample consists of 3902 optical sources and 71 X-ray AGN. Compared to the overall optically selected galaxy population, X-ray AGN are more frequently found in groups at the 99% confidence level. This is partly because AGN are hosted by red luminous galaxies, which are known to reside, on average, in dense environments. Relative to these sources, the excess of X-ray AGN in groups is significant at the 91% level only. Restricting the sample to 0.7<z<0.9 and M_B<-20mag in order to control systematics we find that X-ray AGN represent (4.7\pm1.6) and (4.5\pm1.0)% of the optical galaxy population in groups and in the field respectively. These numbers are consistent with the AGN fraction in low redshift clusters, groups and the field. The results above, although affected by small number statistics, suggest that X-ray AGN are spread over a range of environments, from groups to the field, once the properties of their hosts (e.g. colour, luminosity) are accounted for. There is also tentative evidence, significant at the 98% level, that the field produces more X-ray luminous AGN compared to groups, extending similar results at low redshift to z~1. This trend may be because of either cold gas availability or the nature of the interactions occurring in the denser group environment (i.e. prolonged tidal encounters).Comment: To appear in MNRA

Galaxy Zoo : 3D – crowdsourced bar, spiral, and foreground star masks for MaNGA target galaxies

Funding: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. We gratefully acknowledge the National Science Foundation’s support of the Keck Northeast Astronomy Consortium’s REU program through grants AST-1005024 and AST-1950797, the KINSC (Koshland Integrated Natural Sciences Centre) at Haverford College for Summer Scholar funding, and the Ogden Trust, UK for support for summer undergraduate internships.The challenge of consistent identification of internal structure in galaxies – in particular disc galaxy components like spiral arms, bars, and bulges – has hindered our ability to study the physical impact of such structure across large samples. In this paper we present Galaxy Zoo: 3D (GZ:3D) a crowdsourcing project built on the Zooniverse platform that we used to create spatial pixel (spaxel) maps that identify galaxy centres, foreground stars, galactic bars, and spiral arms for 29 831 galaxies that were potential targets of the MaNGA survey (Mapping Nearby Galaxies at Apache Point Observatory, part of the fourth phase of the Sloan Digital Sky Surveys or SDSS-IV), including nearly all of the 10 010 galaxies ultimately observed. Our crowdsourced visual identification of asymmetric internal structures provides valuable insight on the evolutionary role of non-axisymmetric processes that is otherwise lost when MaNGA data cubes are azimuthally averaged. We present the publicly available GZ:3D catalogue alongside validation tests and example use cases. These data may in the future provide a useful training set for automated identification of spiral arm features. As an illustration, we use the spiral masks in a sample of 825 galaxies to measure the enhancement of star formation spatially linked to spiral arms, which we measure to be a factor of three over the background disc, and how this enhancement increases with radius.Publisher PDFPeer reviewe