Horn Studio Recital

Horn Studio RecitalDaniel Stipe & Hope Armstrong-Erb, pianoTuesday, November 5, 2019 at 7pmSonia Vlahcevic Concert HallSingleton Center for the Performing Arts922 Park VaenueRichmond, Virgini

Metallicity Gradient of a Lensed Face-on Spiral Galaxy at Redshift 1.49

We present the first metallicity gradient measurement for a grand-design face-on spiral galaxy at z~1.5. This galaxy has been magnified by a factor of 22$\times$ by a massive, X-ray luminous galaxy cluster MACS\,J1149.5+2223 at z=0.544. Using the Laser Guide Star Adaptive Optics aided integral field spectrograph OSIRIS on KECK II, we target the Halpha emission and achieve a spatial resolution of 0.1", corresponding to a source plane resolution of 170 pc. The galaxy has well-developed spiral arms and the nebular emission line dynamics clearly indicate a rotationally supported disk with V_{rot}/\sigma~4. The best-fit disk velocity field model yields a maximum rotation of V_{rot} sin{i}=150$\pm$15 km s^{-1}, and a dynamical mass of M_{dyn}=1.3$\pm0.2\times10^{10}csc^2(i) M_{\odot} (within 2.5\,kpc), where the inclination angle i=45$\pm10^{\circ}$. Based on the [NII] and Halpha ratios, we measured the radial chemical abundance gradient from the inner hundreds of parsecs out to ~5 kpc. The slope of the gradient is -0.16$\pm$0.02 dex kpc$^{-1}$, significantly steeper than the gradient of late-type or early-type galaxies in the local universe. If representative of disk galaxies at z~1.5, our results support an "inside-out" disk formation scenario in which early infall/collapse in the galaxy center builds a chemically enriched nucleus, followed by slow enrichment of the disk over the next 9 Gyr.Comment: 13page, 4 figures, ApJL in press (updated version after proof

Strategies for feeding the world more sustainably with organic agriculture

The authors are grateful for the inputs from Caterina Batello, Jan Breithaupt, Carlo Cafiero, Marianna Campeanu, Reto Cumani, Rich Conant, Piero Conforti, Marie-Aude Even, Karen Franken, Andreas Gattinger, Pierre Gerber, Frank Hayer, Jippe Hoogeven, Stefan Hörtenhuber, Mathilde Iweins, John Lantham, Robert Mayo, Eric Meili, Soren Moller, Jamie Morrison, Alexander Müller, Noemi Nemes, Monica Petri, Tim Robinson, Nicolas Sagoff, Henning Steinfeld, Francesco Tubiello, Helga Willer, and thank Robert Home for checking the language. KHE gratefully acknowledges funding from ERC-2010-Stg-263522 (LUISE). The input of PS contributes to the DEVIL project (NE/M021327/1), funded under the Belmont Forum / FACCE-JPI. This paper contributes to the Global Land Project (www.globallandproject.org). The authors acknowledge funding for open access publication by the Institute of Environmental Decisions, Federal Institutes of Technology, Zurich.Peer reviewedPublisher PD

Consumption-Based Conservation Targeting: Linking Biodiversity Loss to Upstream Demand through a Global Wildlife Footprint.

Although most conservation efforts address the direct, local causes of biodiversity loss, effective long-term conservation will require complementary efforts to reduce the upstream economic pressures, such as demands for food and forest products, which ultimately drive these downstream losses. Here, we present a wildlife footprint analysis that links global losses of wild birds to consumer purchases across 57 economic sectors in 129 regions. The United States, India, China, and Brazil have the largest regional wildlife footprints, while per-person footprints are highest in Mongolia, Australia, Botswana, and the United Arab Emirates. A US$100 purchase of bovine meat or rice products occupies approximately 0.1 km2 of wild bird ranges, displacing 1-2 individual birds, for 1 year. Globally significant importer regions, including Japan, the United Kingdom, Germany, Italy, and France, have large footprints that drive wildlife losses elsewhere in the world and represent important targets for consumption-focused conservation attention

The Emission Line Properties of Gravitationally-lensed 1.5 < z < 5 Galaxies

We present and analyse near-infrared spectroscopy for a sample of 28 gravitationally- lensed star-forming galaxies in the redshift range 1.5 < z < 5, observed mostly with the Keck II telescope. With typical magnifications of ~1.5-4 magnitudes, our survey provides a valuable census of star formation rates, gas-phase metallicities and dynamical masses for a representative sample of low luminosity galaxies seen at a formative period in cosmic history. We find less evolution in the mass-metallicity relation compared to earlier work that focused on more luminous systems with z - 2-3, especially in the low mass (- 10^9 Msol) where our sample is - 0.25 dex more metal-rich. We interpret this offset as a result of the lower star formation rates (typically a factor of -10 lower) for a given stellar mass in our sub-luminous systems. Taking this effect into account, we conclude our objects are consistent with a fundamental metallicity relation recently proposed from unlensed observations.Comment: 22 pages, 12 figures, MNRAS, version including proof correction

The galaxy stellar mass-star formation rate relation: Evidence for an evolving stellar initial mass function?

The evolution of the galaxy stellar mass--star formation rate relationship (M*-SFR) provides key constraints on the stellar mass assembly histories of galaxies. For star-forming galaxies, M*-SFR is observed to be fairly tight with a slope close to unity from z~0-2. Simulations of galaxy formation reproduce these trends owing to the generic dominance of smooth and steady cold accretion in these systems. In contrast, the amplitude of the M*-SFR relation evolves markedly differently than in models. Stated in terms of a star formation activity parameter alpha=(M*/SFR)/(t_H-1 Gyr), models predict a constant alpha~1 out to redshifts z=4+, while the observed M*-SFR relation indicates that alpha increases by X3 from z~2 until today. The low alpha at high-z not only conflicts with models, but is also difficult to reconcile with other observations of high-z galaxies. Systematic biases could significantly affect measurements of M* and SFR, but detailed considerations suggest that none are obvious candidates to reconcile the discrepancy. A speculative solution is considered in which the stellar initial mass function (IMF) evolves towards more high-mass star formation at earlier epochs. Following Larson, a model is investigated in which the characteristic mass Mhat where the IMF turns over increases with redshift. The observed and predicted M*-SFR evolution may be brought into agreement if Mhat=0.5(1+z)^2 Mo out to z~2. Such evolution broadly matches recent observations of cosmic stellar mass growth, and the resulting z=0 cumulative IMF is similar to the paunchy IMF favored by Fardal et al to reconcile the observed cosmic star formation history with present-day fossil light measures. [abridged]Comment: 14 pages, MNRAS, accepted version. Significant expansion of discussion; includes comparisons to new observation

Excess AGN Activity in the z=2.30 Protocluster in HS 1700+64

We present the results of spectroscopic, narrow-band and X-ray observations of a z=2.30 protocluster in the field of the QSO HS 1700+643. Using a sample of BX/MD galaxies, which are selected to be at z~2.2-2.7 by their rest-frame ultraviolet colours, we find that there are 5 protocluster AGN which have been identified by characteristic emission-lines in their optical/near-IR spectra; this represents an enhancement over the field significant at ~98.5 per cent confidence. Using a ~200 ks Chandra/ACIS-I observation of this field we detect a total of 161 X-ray point sources to a Poissonian false-probability limit of 4x10^{-6} and identify 8 of these with BX/MD galaxies. Two of these are spectroscopically confirmed protocluster members and are also classified as emission-line AGN. When compared to a similarly selected field sample the analysis indicates this is also evidence for an enhancement of X-ray selected BX/MD AGN over the field, significant at ~99 per cent confidence. Deep Lya narrow-band imaging reveals that a total of 4/123 Lya emitters (LAEs) are found to be associated with X-ray sources, with two of these confirmed protocluster members and one highly likely member. We do not find a significant enhancement of AGN activity in this LAE sample over that of the field (result significant at only 87 per cent confidence). The X-ray emitting AGN fractions for the BX/MD and LAE samples are found to be 6.9_{-4.4}^{+9.2} and 2.9_{-1.6}^{+2.9} per cent, respectively, for protocluster AGN with L_{2-10 keV}>4.6x10^{43} erg s^{-1} at z=2.30. These findings are similar to results from the z=3.09 protocluster in the SSA 22 field found by Lehmer et al. (2009), in that both suggest AGN activity is favoured in dense environments at z>2.Comment: 8 pages, 2 figures. Accepted for publication in MNRAS

A Strategy to Measure the Dark Energy Equation of State using the HII galaxy Hubble Relation & X-ray AGN Clustering: Preliminary Results

We explore the possibility of setting stringent constraints to the Dark Energy equation of state using alternative cosmic tracers like: (a) the Hubble relation using HII galaxies, which can be observed at much higher redshifts (z~3.5) than those currently traced by SNIa samples, and (b) the large-scale structure using the clustering of X-ray selected AGN,which have a redshift distribution peaking at z~1. We use extensive Monte-Carlo simulations to define the optimal strategy for the recovery of the dark-energy equation of state using the high redshift (z~2) Hubble relation, but accounting also for the effects of gravitational lensing, which for such high redshifts can significantly affect the derived cosmological constraints. Based on a "Figure of Merit" analysis, we provide estimates for the number of 2<z<3.5 tracers needed to reduce the cosmological solution space, presently provided by the Constitution SNIa set, by a desired factor. We find that it is much more efficient to increase the number of tracers than to reduce their individual uncertainties. Finally, we propose a framework to put constraints on the dark energy equation of state by using the joint likelihood of the X-ray AGN clustering and of the Hubble relation cosmological analyses. A preliminary joint analysis using the X-ray AGN clustering of the 2XMM survey and the Hubble relation of the Constitution SNIa set provide: Omega_m= 0.31+-0.01 and w=-1.06+-0.05. We also find that the joint SNIa-2XMM analysis provides significantly more stringent cosmological constraints, increasing the Figure of Merit by a factor ~2, with respect to that of the joint SNIa-BAO analysis.Comment: MNRAS in press, 12 colour figure

LBT and Spitzer Spectroscopy of Star-Forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators

We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample was selected to represent pure, actively star-forming systems, absent of active galactic nuclei. The large lensing magnifications result in high signal-to-noise spectra that can probe faint IR recombination lines, including Pa-alpha and Br-alpha at high redshifts. The sample was augmented by three lensed galaxies with similar suites of unpublished data and observations from the literature, resulting in the final sample of seven galaxies. We use the IR recombination lines in conjunction with H-alpha observations to probe the extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from ~0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z ~ 2 must take careful count of extinction in the most IR luminous galaxies. We also measure extinction by comparing SFR estimates from optical emission lines with those from far-IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 < z < 3. Without correcting for dust extinction, the H-alpha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2 micron PAH emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, ~0.2 dex scatter is observed.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 8 figure

Experimental evidence that livestock grazing intensity affects cyclic vole population regulation processes

Peer reviewedPublisher PD