Now showing items 21-40 of 11705

    • Toward Improved Probabilistic Predictions for Flood Forecasts Generated Using Deterministic Models

      Jiang, Xiaolei; Gupta, Hoshin V.; Liang, Zhongmin; Li, Binquan; Univ Arizona, Dept Hydrol & Atmospher Sci (AMER GEOPHYSICAL UNION, 2019-11-20)
      Uncertainties in flood forecasts are inevitable, and the key issue is to develop probabilistic predictions so that the predictive uncertainty (PU) bounds can be estimated. We develop and test a general method for probabilistic forecasting and PU estimation that is based on a theoretical and practical analysis of the actual nature of the model residuals, which reveals that the residual mean, standard deviation, and distributional form can all vary with time. Our approach is to condition the nature of the residual distribution on the magnitude of the corresponding streamflow value, but other kinds of conditioning are also possible. Using real data, we illustrate seven progressively more realistic sets of assumptions regarding the model residuals, ranging from homogenous Gaussian to fully heterogeneous non-Gaussian. Our results show that the estimated probabilistic predictions become progressively better as the assumptions better conform to the actual properties of the residuals. As benchmarks, we compare against results from the state-of-the-art power transformation approach. Our method is generally applicable to any situation where a deterministic model is used to generate predictions, and where empirical probabilistic predictions are required without developing a stochastic version of that model.
    • No significant correlation between radial velocity planet presence and debris disc properties

      Yelverton, Ben; Kennedy, Grant M; Su, Kate Y L; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2020-05-13)
      We investigate whether the tentative correlation between planets and debris discs which has been previously identified can be confirmed at high significance. We compile a sample of 201 stars with known planets and existing far-infrared observations. The sample is larger than those studied previously since we include targets from an unpublished Herschel survey of planet hosts. We use spectral energy distribution modelling to characterize Kuiper belt analogue debris discs within the sample, then compare the properties of the discs against a control sample of 294 stars without known planets. Survival analysis suggests that there is a significant (p similar to 0.002) difference between the disc fractional luminosity distributions of the two samples. However, this is largely a result of the fact that the control sample contains a higher proportion of close binaries and of later-type stars; both of these factors are known to reduce disc detection rates. Considering only Sun-like stars without close binary companions in each sample greatly reduces the significance of the difference (p similar to 0.3). We also find no evidence for a difference in the disc fractional luminosities of stars hosting planets more or less massive than Saturn (p similar to 0.9). Finally, we find that the planet hosts have cooler discs than the control stars, but this is likely a detection bias, since the warmest discs in the control sample are also the faintest, and would thus be undetectable around the more distant planet hosts. Considering only discs in each sample that could have been detected around a typical planet host, we find p similar to 0.07 for the temperatures.
    • JINGLE – IV. Dust, H i gas, and metal scaling laws in the local Universe

      De Looze, I; Lamperti, I; Saintonge, A; Relaño, M; Smith, M W L; Clark, C J R; Wilson, C D; Decleir, M; Jones, A P; Kennicutt, R C; et al. (OXFORD UNIV PRESS, 2020-06-02)
      Scaling laws of dust, HI gas, and metal mass with stellar mass, specific star formation rate, and metallicity are crucial to our understanding of the build-up of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass (M-HI/M-star) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - including stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multidimensional parameter space. We find that these scaling laws for galaxies with -1.0 less than or similar to log M-HI/M-star less than or similar to 0 can be reproduced using closed-box models with high fractions (37-89 per cent) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies (subset of = 30-40), and long dust lifetimes (1-2 Gyr). The models have present-day dust masses with similar contributions from stellar sources (50-80 per cent) and grain growth (20-50 per cent). Over the entire lifetime of these galaxies, the contribution from stardust (>90 per cent) outweighs the fraction of dust grown in the interstellar medium (<10 per cent). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth time-scales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium.
    • Miocene C4 Grassland Expansion as Recorded by the Indus Fan

      Feakins, Sarah J.; Liddy, Hannah M.; Tauxe, Lisa; Galy, Valier; Feng, Xiaojuan; Tierney, Jessica E.; Miao, Yunfa; Warny, Sophie; Univ Arizona, Dept Geosci (AMER GEOPHYSICAL UNION, 2020-05-07)
      In the late Miocene, grasslands spread across the forested floodplains of the Himalayan foreland, but the causes of the ecological transition are still debated. Recent seafloor drilling by the International Ocean Discovery Program (IODP) provides an opportunity to study the transition across a larger region as archived in the Indus submarine fan. We present a multiproxy study of past vegetation change based on analyses of the carbon isotopic composition (delta C-13) of bulk organic carbon, plant waxn-alkanes andn-alkanoic acids, and quantification of lignin phenols, charcoal, and pollen. We analyze the hydrogen isotopic composition (delta D) of plant wax to reconstruct precipitation delta D. We use the Branched and Isoprenoid Tetraether (BIT) index to diagnose shifts between terrestrial versus marine lipid inputs between turbidite and hemipelagic sediments. We reconstruct ocean temperatures using the TEX(86)index only where marine lipids dominate. We find evidence for the late Miocene grassland expansion in both facies, confirming this was a regional ecosystem transformation. Turbidites contain dominantly terrestrial matter from the Indus catchment (D-depleted plant wax), delivered via fluvial transport as shown by the presence of lignin. In contrast, hemipelagic sediments lack lignin and bear D-enriched plant wax consistent with wind-blown inputs from the Indian peninsula; these show a 7.4-7.2 Ma expansion of C(4)grasslands on the Indian subcontinent. Within each facies, we find no clear change in delta D values across the late Miocene C(4)expansion, implying consistent distillation of rainfall by monsoon dynamics. Yet, a cooling in the Arabian Sea is coincident with the C(4)expansion.
    • Formation dynamics of exciton-polariton vortices created by nonresonant annular pumping

      Berger, Bernd; Schmidt, Daniel; Ma, Xuekai; Schumacher, Stefan; Schneider, Christian; Höfling, Sven; Aßmann, Marc; Univ Arizona, Coll Opt Sci (AMER PHYSICAL SOC, 2020-06-24)
      We study the spontaneous formation of exciton-polariton vortices in an all-optical nonresonantly excited annular trap, which is formed by ring-shaped subpicosecond laser pulses. Since the light emitted by these vortices carries orbital angular momentum (OAM) corresponding to their topological charge, we apply a dedicated OAM spectroscopy technique to detect the OAM of the measurement signal with picosecond time resolution. This allows us to identify the formation of OAM modes and investigate the dynamics of the vortex formation process. We also study the power dependence of this process and how the ring diameter influences the formation of OAM modes.
    • Relationships Between Supermicrometer Sea Salt Aerosol and Marine Boundary Layer Conditions: Insights From Repeated Identical Flight Patterns

      Schlosser, Joseph S.; Dadashazar, Hossein; Edwards, Eva‐Lou; Hossein Mardi, Ali; Prabhakar, Gouri; Stahl, Connor; Jonsson, Haflidi H.; Sorooshian, Armin; Univ Arizona, Dept Chem & Environm Engn; Dept Hydrol & Atmospher Sci (AMER GEOPHYSICAL UNION, 2020-05-25)
      The MONterey Aerosol Research Campaign (MONARC) in May-June 2019 featured 14 repeated identical flights off the California coast over the open ocean at the same time each flight day. The objective of this study is to use MONARC data along with machine learning analysis to evaluate relationships between both supermicrometer sea salt aerosol number (N->1) and volume (V->1) concentrations and wind speed, wind direction, sea surface temperature (SST), ambient temperature (T-amb), turbulent kinetic energy (TKE), relative humidity (RH), marine boundary layer (MBL) depth, and drizzle rate. Selected findings from this study include the following: (i) Near surface (<60 m) N(>1)and V(>1)concentration ranges were 0.1-4.6 cm(-3)and 0.3-28.2 mu m(3) cm(-3), respectively; (ii) four meteorological regimes were identified during MONARC with each resulting in different N(>1)and V(>1)concentrations and also varying horizontal and vertical profiles; (iii) the relative predictive strength of the MBL properties varies depending on predicting N(>1)or V->1, with MBL depth being more highly ranked for predicting N(>1)and with TKE being higher for predicting V->1; (iv) MBL depths >400 m (<200 m) often correspond to lower (higher) N(>1)and V(>1)concentrations; (v) enhanced drizzle rates coincide with reduced N(>1)and V(>1)concentrations; (vi) N(>1)and V(>1)concentrations exhibit an overall negative relationship with SST and RH and an overall positive relationship with T-amb; and (vii) wind speed and direction were relatively weak predictors of N(>1)and V->1.
    • a-numbers of curves in Artin–Schreiercovers

      Booher, Jeremy; Cais, Bryden; Univ Arizona, Dept Math (MATHEMATICAL SCIENCE PUBL, 2020-06-01)
      Let pi : Y -> X be a branched Z/pZ-cover of smooth, projective, geometrically connected curves over a perfect field of characteristic p > 0. We investigate the relationship between the a-numbers of Y and X and the ramification of the map pi. This is analogous to the relationship between the genus (respectively p-rank) of Y and X given the Riemann-Hurwitz (respectively Deuring-Shafarevich) formula. Except in special situations, the a-number of Y is not determined by the a-number of X and the ramification of the cover, so we instead give bounds on the a-number of Y. We provide examples showing our bounds are sharp. The bounds come from a detailed analysis of the kernel of the Cartier operator.
    • Serine 319 phosphorylation is necessary and sufficient to induce a Cx37 conformation that leads to arrested cell cycling

      Taylor, Samantha-Su Z.; Jacobsen, Nicole L.; Pontifex, Tasha K.; Langlais, Paul; Burt, Janis M.; Univ Arizona, Coll Med; Univ Arizona, Dept Physiol; Univ Arizona, Dept Med (COMPANY BIOLOGISTS LTD, 2020-06-18)
      Connexin 37 (Cx37; protein product of GJA4) expression profoundly suppresses proliferation of rat insulinoma (Rin) cells in a manner dependent on gap junction channel (GJCh) functionality and the presence and phosphorylation status of its C-terminus (CT). In Rin cells, growth is arrested upon induced Cx37 expression and serine 319 (S319) is frequently phosphorylated. Here, we show that preventing phosphorylation at this site (alanine substitution; S319A) relieved Cx37 of its growth-suppressive effect whereas mimicking phosphorylation at this site (aspartate substitution; S319D) enhanced the growth-suppressive properties of Cx37. Like wild-type Cx37 (Cx37-WT), Cx37-S319D GJChs and hemichannels (HChs) preferred the closed state, rarely opening fully, and gated slowly. In contrast, Cx37-S319A channels preferred open states, opened fully and gated rapidly. These data indicate that phosphorylation-dependent conformational differences in Cx37 protein and channel function underlie Cx37-induced growth arrest versus growth-permissive phenotypes. That the closed state of Cx37-WT and Cx37-S319D GJChs and HChs favors growth arrest suggests that rather than specific permeants mediating cell cycle arrest, the closed conformation instead supports interaction of Cx37 with growth regulatory proteins that result in growth arrest.
    • From the bulge to the outer disc: StarHorse stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys

      Queiroz, A. B. A.; Anders, F.; Chiappini, C.; Khalatyan, A.; Santiago, B. X.; Steinmetz, M.; Valentini, M.; Miglio, A.; Bossini, D.; Barbuy, B.; et al. (EDP SCIENCES S A, 2020-06-15)
      We combine high-resolution spectroscopic data from APOGEE-2 survey Data Release 16 (DR16) with broad-band photometric data from several sources as well as parallaxes from Gaia Data Release 2 (DR2). Using the Bayesian isochrone-fitting code StarHorse, we derived the distances, extinctions, and astrophysical parameters for around 388 815 APOGEE stars. We achieve typical distance uncertainties of similar to 6% for APOGEE giants, similar to 2% for APOGEE dwarfs, and extinction uncertainties of similar to 0.07 mag, when all photometric information is available, and similar to 0.17 mag if optical photometry is missing. StarHorse uncertainties vary with the input spectroscopic catalogue, available photometry, and parallax uncertainties. To illustrate the impact of our results, we show that thanks to Gaia DR2 and the now larger sky coverage of APOGEE-2 (including APOGEE-South), we obtain an extended map of the Galactic plane. We thereby provide an unprecedented coverage of the disc close to the Galactic mid-plane (|Z(Gal)| < 1 kpc) from the Galactic centre out to R-Gal<similar to>20 kpc. The improvements in statistics as well as distance and extinction uncertainties unveil the presence of the bar in stellar density and the striking chemical duality in the innermost regions of the disc, which now clearly extend to the inner bulge. We complement this paper with distances and extinctions for stars in other public released spectroscopic surveys: 324 999 in GALAH DR2, 4 928 715 in LAMOST DR5, 408 894 in RAVE DR6, and 6095 in GES DR3.
    • Pebble-driven planet formation around very low-mass stars and brown dwarfs

      Liu, Beibei; Lambrechts, Michiel; Johansen, Anders; Pascucci, Ilaria; Henning, Thomas; Univ Arizona, Lunar & Planetary Lab (EDP SCIENCES S A, 2020-06-18)
      We conduct a pebble-driven planet population synthesis study to investigate the formation of planets around very low-mass stars and brown dwarfs in the (sub)stellar mass range between 0.01 M(circle dot)and 0.1 M-circle dot. Based on the extrapolation of numerical simulations of planetesimal formation by the streaming instability, we obtain the characteristic mass of the planetesimals and the initial mass of the protoplanet (largest body from the planetesimal populations), in either the early self-gravitating phase or the later non-self-gravitating phase of the protoplanetary disk evolution. We find that the initial protoplanets form with masses that increase with host mass and orbital distance, and decrease with age. Around late M-dwarfs of 0.1 M-circle dot, these protoplanets can grow up to Earth-mass planets by pebble accretion. However, around brown dwarfs of 0.01 M-circle dot, planets do not grow to the masses that are greater than Mars when the initial protoplanets are born early in self-gravitating disks, and their growth stalls at around 0.01 Earth-mass when they are born late in non-self-gravitating disks. Around these low-mass stars and brown dwarfs we find no channel for gas giant planet formation because the solid cores remain too small. When the initial protoplanets form only at the water-ice line, the final planets typically have greater than or similar to 15% water mass fraction. Alternatively, when the initial protoplanets form log-uniformly distributed over the entire protoplanetary disk, the final planets are either very water rich (water mass fraction greater than or similar to 15%) or entirely rocky (water mass fraction less than or similar to 5%).
    • The GOGREEN Survey: A deep stellar mass function of cluster galaxies at 1.0 < z < 1.4 and the complex nature of satellite quenching

      van der Burg, Remco F. J.; Rudnick, Gregory; Balogh, Michael L.; Muzzin, Adam; Lidman, Chris; Old, Lyndsay J.; Shipley, Heath; Gilbank, David; McGee, Sean; Biviano, Andrea; et al. (EDP SCIENCES S A, 2020-06-23)
      We study the stellar mass functions (SMFs) of star-forming and quiescent galaxies in 11 galaxy clusters at 1.0<z<1.4 drawn from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. Based on more than 500 h of Gemini/GMOS spectroscopy and deep multi-band photometry taken with a range of observatories, we probe the SMFs down to a stellar mass limit of 10(9.7) M-circle dot (10(9.5) M-circle dot for star-forming galaxies). At this early epoch, the fraction of quiescent galaxies is already highly elevated in the clusters compared to the field at the same redshift. The quenched fraction excess (QFE) represents the fraction of galaxies that would be star-forming in the field but are quenched due to their environment. The QFE is strongly mass dependent, and increases from similar to 30% at M-star=10(9.7) M-circle dot to similar to 80% at M-star=10(11.0) M-circle dot. Nonetheless, the shapes of the SMFs of the two individual galaxy types, star-forming and quiescent galaxies, are identical between cluster and field to high statistical precision. Nevertheless, along with the different quiescent fractions, the total galaxy SMF is also environmentally dependent, with a relative deficit of low-mass galaxies in the clusters. These results are in stark contrast with findings in the local Universe, and therefore require a substantially different quenching mode to operate at early times. We discuss these results in light of several popular quenching models.
    • Three mechanisms for bar thickening

      Sellwood, J A; Gerhard, Ortwin; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2020-05-18)
      We present simulations of bar-unstable stellar discs in which the bars thicken into box/peanut shapes. Detailed analysis of the evolution of each model revealed three different mechanisms for thickening the bars. The first mechanism is the well-known buckling instability, the second is the vertical excitation of bar orbits by passage through the 2:1 vertical resonance, and the third is a gradually increasing fraction of bar orbits trapped into this resonance. Since bars in many galaxies may have formed and thickened long ago, we have examined the models for fossil evidence in the velocity distribution of stars in the bar, finding a diagnostic to discriminate between a bar that had buckled from the other two mechanisms.
    • Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18

      James, Bethan L; Kumari, Nimisha; Emerick, Andrew; Koposov, Sergey E; McQuinn, Kristen B W; Stark, Daniel P; Belokurov, Vasily; Maiolino, Roberto; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2020-05-08)
      Deciphering the distribution of metals throughout galaxies is fundamental in our understanding of galaxy evolution. Nearby, low-metallicity, star-forming dwarf galaxies, in particular, can offer detailed insight into the metal-dependent processes that may have occurred within galaxies in the early Universe. Here, we present VLT/MUSE observations of one such system, JKB 18, a blue diffuse dwarf galaxy with a metallicity of only 12 + log(O/H)=7.6 +/- 0.2 (similar to 0.08 Z(circle dot)). Using high spatial resolution integral-field spectroscopy of the entire system, we calculate chemical abundances for individual H?ii regions using the direct method and derive oxygen abundance maps using strong-line metallicity diagnostics. With large-scale dispersions in O/H, N/H, and N/O of similar to 0.5-0.6 dex and regions harbouring chemical abundances outside this 1 sigma distribution, we deem JKB 18 to be chemically inhomogeneous. We explore this finding in the context of other chemically inhomogeneous dwarf galaxies and conclude that neither the accretion of metal-poor gas, short mixing time-scales or self-enrichment from WolfRayet stars are accountable. Using a galaxy-scale, multiphase, hydrodynamical simulation of a low-mass dwarf galaxy, we find that chemical inhomogeneities of this level may be attributable to the removal of gas via supernovae and the specific timing of the observations with respect to star formation activity. This study not only draws attention to the fact that dwarf galaxies can be chemically inhomogeneous, but also that the methods used in the assessment of this characteristic can be subject to bias.
    • Asymmetric surface brightness structure of caustic crossing arc in SDSS J1226+2152: a case for dark matter substructure

      Dai, Liang; Kaurov, Alexander A; Sharon, Keren; Florian, Michael; Miralda-Escudé, Jordi; Venumadhav, Tejaswi; Frye, Brenda; Rigby, Jane R; Bayliss, Matthew; Univ Arizona, Dept Astron, Steward Observ (OXFORD UNIV PRESS, 2020-05-15)
      We study the highly magnified arc SGAS J122651.3+215220 caused by a star-forming galaxy at z(s) = 2.93 crossing the lensing caustic cast by the galaxy cluster SDSS J1226+2152 (z(l) = 0.43), using Hubble Space Telescope observations. We report in the arc several asymmetric surface brightness features whose angular separations are a fraction of an arcsecond from the lensing critical curve and appear to be highly but unequally magnified image pairs of underlying compact sources, with one brightest pair having clear asymmetry consistently across four filters. One explanation of unequal magnification is microlensing by intracluster stars, which induces independent flux variations in the images of individual or groups of source stars in the lensed galaxy. For a second possibility, intracluster dark matter subhaloes invisible to telescopes effectively perturb lensing magnifications near the critical curve and give rise to persistently unequal image pairs. Our modelling suggests, at least for the most prominent identified image pair, that the microlensing hypothesis is in tension with the absence of notable asymmetry variation over a six-year baseline, while subhaloes of similar to 10(6) - 10(8) M-circle dot anticipated from structure formation with cold dark matter typically produce stationary and sizable asymmetries. We judge that observations at additional times and more precise lens models are necessary to stringently constrain temporal variability and robustly distinguish between the two explanations. The arc under this study is a scheduled target of a Director's Discretionary Early Release Science program of the James Webb Space Telescope, which will provide deep images and a high-resolution view with integral field spectroscopy.
    • Dark Energy Survey identification of a low-mass active galactic nucleus at redshift 0.823 from optical variability

      Guo, Hengxiao; Burke, Colin J; Liu, Xin; Phadke, Kedar A; Zhang, Kaiwen; Chen, Yu-Ching; Gruendl, Robert A; Lidman, Christopher; Shen, Yue; Morganson, Eric; et al. (OXFORD UNIV PRESS, 2020-06-23)
      We report the identification of a low-mass active galactic nucleus (AGN), DES J0218-0430, in a redshift z = 0.823 galaxy in the Dark Energy Survey (DES) Supernova field. We select DES J0218-0430 as an AGN candidate by characterizing its long-term optical variability alone based on DES optical broad-band light curves spanning over 6 yr. An archival optical spectrum from the fourth phase of the Sloan Digital Sky Survey shows both broad MgII and broad H beta lines, confirming its nature as a broad-line AGN. Archival XMM-Newton X-ray observations suggest an intrinsic hard X-ray luminosity of L2-12 keV approximate to 7.6 +/- 0.4 x 10(43) erg s(-1), which exceeds those of the most X-ray luminous starburst galaxies, in support of an AGN driving the optical variability. Based on the broad H beta from SDSS spectrum, we estimate a virial black hole (BH) mass of M-circle approximate to 10(6.43) - 10(6.72) M-circle dot (with the error denoting the systematic uncertainty from different calibrations), consistent with the estimation from OzDES, making it the lowest mass AGN with redshift > 0.4 detected in optical. We estimate the host galaxy stellar mass to be M-* approximate to 10(10.5 +/- 0.3) M-circle dot based on modelling the multiwavelength spectral energy distribution. DES J0218-0430 extends the M-circle-M-* relation observed in luminous AGNs at z similar to 1 to masses lower than being probed by previous work. Our work demonstrates the feasibility of using optical variability to identify low-mass AGNs at higher redshift in deeper synoptic surveys with direct implications for the upcoming Legacy Survey of Space and Time at Vera C. Rubin Observatory.
    • Linear ubiquitin assembly complex regulates lung epithelial-driven responses during influenza infection

      Brazee, Patricia L; Morales-Nebreda, Luisa; Magnani, Natalia D; Garcia, Joe G N; Misharin, Alexander V; Ridge, Karen M; Budinger, G R Scott; Iwai, Kazuhiro; Dada, Laura A; Sznajder, Jacob I; et al. (AMER SOC CLINICAL INVESTIGATION INC, 2020-01-27)
      Influenza A virus (IAV) is among the most common causes of pneumonia-related death worldwide. Pulmonary epithelial cells are the primary target for viral infection and replication and respond by releasing inflammatory mediators that recruit immune cells to mount the host response. Severe lung injury and death during IAV infection result from an exuberant host inflammatory response. The linear ubiquitin assembly complex (LUBAC), composed of SHARPIN, HOIL-1L, and HOIP, is a critical regulator of NF-kappa B-dependent inflammation. Using mice with lung epithelial-specific deletions of HOIL-1L or HOIP in a model of IAV infection, we provided evidence that, while a reduction in the inflammatory response was beneficial, ablation of the LUBAC-dependent lung epithelial-driven response worsened lung injury and increased mortality. Moreover, we described a mechanism for the upregulation of HOIL-1L in infected and noninfected cells triggered by the activation of type I IFN receptor and mediated by IRF1, which was maladaptive and contributed to hyperinflammation. Thus, we propose that lung epithelial LUBAC acts as a molecular rheostat that could be selectively targeted to modulate the immune response in patients with severe IAV-induced pneumonia.
    • The GOGREEN survey: the environmental dependence of the star-forming galaxy main sequence at 1.0 < z < 1.5

      Old, Lyndsay J; Balogh, Michael L; van der Burg, Remco F J; Biviano, Andrea; Yee, Howard K C; Pintos-Castro, Irene; Webb, Kristi; Muzzin, Adam; Rudnick, Gregory; Vulcani, Benedetta; et al. (OXFORD UNIV PRESS, 2020-03-04)
      We present results on the environmental dependence of the star-forming galaxy main sequence in 11 galaxy cluster fields at 1.0 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early Environments Survey (GOGREEN) survey. We use a homogeneously selected sample of field and cluster galaxies whose membership is derived from dynamical analysis. Using [O II]-derived star formation rates (SFRs), we find that cluster galaxies have suppressed SFRs at fixed stellar mass in comparison to their field counterparts by a factor of 1.4 +/- 0.1 (similar to 3.3 sigma) across the stellar mass range: 9.0 < log (M-*/M-circle dot) < 11.2. We also find that this modest suppression in the cluster galaxy star-forming main sequence is mass and redshift dependent: the difference between cluster and field increases towards lower stellar masses and lower redshift. When comparing the distribution of cluster and field galaxy SFRs to the star-forming main sequence, we find an overall shift towards lower SFRs in the cluster population, and note the absence of a tail of high SFR galaxies as seen in the field. Given this observed suppression in the cluster galaxy star-forming main sequence, we explore the implications for several scenarios such as formation time differences between cluster and field galaxies, and environmentally induced star formation quenching and associated time-scales.
    • Dark Energy Survey Year 1 Results: Wide-field mass maps via forward fitting in harmonic space

      Mawdsley, B; Bacon, D; Chang, C; Melchior, P; Rozo, E; Seitz, S; Jeffrey, N; Gatti, M; Gaztanaga, E; Gruen, D; et al. (OXFORD UNIV PRESS, 2020-03-09)
      We present new wide-field weak lensing mass maps for the Year 1 Dark Energy Survey (DES) data, generated via a forward fitting approach. This method of producing maps does not impose any prior constraints on the mass distribution to be reconstructed. The technique is found to improve the map reconstruction on the edges of the field compared to the conventional Kaiser-Squires method, which applies a direct inversion on the data; our approach is in good agreement with the previous direct approach in the central regions of the footprint. The mapping technique is assessed and verified with tests on simulations; together with the Kaiser-Squires method, the technique is then applied to data from the DES Year 1 data and the differences between the two methods are compared. We also produce the first DES measurements of the convergence Minkowski functionals and compare them to those measured in simulations.
    • STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408−5354

      Shajib, A J; Birrer, S; Treu, T; Agnello, A; Buckley-Geer, E J; Chan, J H H; Christensen, L; Lemon, C; Lin, H; Millon, M; et al. (OXFORD UNIV PRESS, 2020-03-28)
      We present a blind time-delay cosmographic analysis for the lens system DES J0408-5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine themeasured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the 'effective' time-delay distance corresponding to the redshifts of the deflector and the lensed quasar D-Delta t(eff) = 3382(-115)(+146) Mpc and the angular diameter distance to the deflector D-d = 1711(-280)(+376) Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H-0 = 74.2(-3.0)(+2.7) km s(-1) Mpc(-1) assuming a flat Lambda CDM cosmology and a uniform prior for Omega(m) as Omega(m) similar to U(0.05, 0.5). This measurement gives the most precise constraint on H-0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H-0 Lenses in COSMOGRAIL's Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H-0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2 sigma discrepancy from the cosmic microwave background measurement.
    • The mystery of photometric twins DES17X1boj and DES16E2bjy

      Pursiainen, M; Gutiérrez, C P; Wiseman, P; Childress, M; Smith, M; Frohmaier, C; Angus, C; Castro Segura, N; Kelsey, L; Sullivan, M; et al. (OXFORD UNIV PRESS, 2020-04-13)
      We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (M-r = -15.4 and -17.9, respectively). The light-curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data are well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800 km s(-1) for DES17X1boj and 4800 km s(-1) for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity Ca II absorption (v approximate to 9400 km s(-1)) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light-curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterize the progenitors.