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3 results on '"Tepper-García, T"'

1. The GALAH survey: tracing the Galactic disc with open clusters.

Author

Spina, L, Ting, Y-S, De Silva, G M, Frankel, N, Sharma, S, Cantat-Gaudin, T, Joyce, M, Stello, D, Karakas, A I, Asplund, M B, Nordlander, T, Casagrande, L, D'Orazi, V, Casey, A R, Cottrell, P, Tepper-García, T, Baratella, M, Kos, J, Čotar, K, and Bland-Hawthorn, J

Subjects
OPEN clusters of stars, GALACTIC evolution, GALAXY clusters, FUNCTION spaces, STELLAR dynamics, ASTROMETRY, STAR clusters
Abstract

Open clusters are unique tracers of the history of our own Galaxy's disc. According to our membership analysis based on Gaia astrometry, out of the 226 potential clusters falling in the footprint of the GALactic Archaeology with HERMES (GALAH) survey or the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey, we find that 205 have secure members that were observed by at least one of the surveys. Furthermore, members of 134 clusters have high-quality spectroscopic data that we use to determine their chemical composition. We leverage this information to study the chemical distribution throughout the Galactic disc of 21 elements, from C to Eu. The radial metallicity gradient obtained from our analysis is −0.076 ± 0.009 dex kpc−1, which is in agreement with previous works based on smaller samples. Furthermore, the gradient in the [Fe/H]–guiding radius (r guid) plane is −0.073 ± 0.008 dex kpc−1. We show consistently that open clusters trace the distribution of chemical elements throughout the Galactic disc differently than field stars. In particular, at the given radius, open clusters show an age–metallicity relation that has less scatter than field stars. As such scatter is often interpreted as an effect of radial migration, we suggest that these differences are due to the physical selection effect imposed by our Galaxy: clusters that would have migrated significantly also had higher chances to get destroyed. Finally, our results reveal trends in the [X/Fe]– r guid–age space, which are important to understand production rates of different elements as a function of space and time. [ABSTRACT FROM AUTHOR]

Published
2021
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2. Absorption signatures of warm-hot gas at low redshift: NeVIII

Author

Tepper-García, T., Richter, P., Schaye, J., Tepper-García, T, Richter, P, and Schaye, J

Subjects
Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Cosmic Origins Spectrograph, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Institut für Physik und Astronomie, FOS: Physical sciences, Astronomy and Astrophysics, Quasar, Plasma, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Redshift, Spectral line, Baryon, Space and Planetary Science, 0103 physical sciences, Content (measure theory), Absorption (logic), Atomic physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

At z14), like those recently detected by HST/COS, are found to arise in higher density gas (log n>-4, log T=5.75). NeVIII cloudlets harbour only 1 per cent of the cosmic baryon budget. The baryon content of the surrounding gas (which has similar densities and temperatures as the NeVIII cloudlets) is a factor 1/c_L higher. We conclude that NeVIII absorbers are robust probes of shock-heated diffuse gas, but that spectra with signal-to-noise ratios S/N>100 would be required to detect the bulk of the baryons in warm-hot gas., 19 pages, 10 figures; MNRAS in press; minor changes with respect to v1

Published
2013

3. Absorption signatures of warm-hot gas at low redshift : broad HI Lyα absorbers

Author

Tepper-García, T., Richter, P., Schaye, J., Booth, C.M., Dalla Vecchia, C., and Theuns, Tom

Subjects
numerical [Methods], absorption lines [Quasars], Physics, theory. [Cosmology], Astrophysics::Cosmology and Extragalactic Astrophysics, formation [Galaxies], Astrophysics::Galaxy Astrophysics, Intergalactic medium
Abstract

We investigate the physical state of H?i absorbing gas at low redshift (z = 0.25) using a subset of cosmological, hydrodynamic simulations from the OverWhelmingly Large Simulations project, focusing in particular on broad (bHI=40 km s-1) H?i Lya absorbers (BLAs), which are believed to originate in shock-heated gas in the warm-hot intergalactic medium (WHIM). Our fiducial model, which includes radiative cooling by heavy elements and feedback by supernovae and active galactic nuclei, predicts that by z = 0.25 nearly 60?per cent of the gas mass ends up at densities and temperatures characteristic of the WHIM and we find that half of this fraction is due to outflows. The standard H?i observables (distribution of H?i column densities NH?I, distribution of Doppler parameters bHI, bHINH?I correlation) and the BLA line number density predicted by our simulations are in remarkably good agreement with observations. BLAs arise in gas that is hotter, more highly ionized and more enriched than the gas giving rise to typical Lya forest absorbers. The majority of the BLAs arise in warm-hot [log?(T/?K) similar to 5] gas at low (log?? < 1.5) overdensities. On average, thermal broadening accounts for at least 60?per cent of the BLA linewidth, which in turn can be used as a rough indicator of the thermal state of the gas. Detectable BLAs account for only a small fraction of the true baryon content of the WHIM at low redshift. In order to detect the bulk of the mass in this gas phase, a sensitivity at least one order of magnitude better than achieved by current ultraviolet spectrographs is required. We argue that BLAs mostly trace gas that has been shock heated and enriched by outflows and that they therefore provide an important window on a poorly understood feedback process.

Published
2012

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