@article{TepperGarciaRichterSchaye2013,
  author    = {Tepper-Garcia, Thor and Richter, Philipp and Schaye, Joop},
  title     = {Absorption signatures of warm-hot gas at low redshift - ne viii},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {436},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0035-8711},
  doi       = {10.1093/mnras/stt1712},
  pages     = {2063 -- 2081},
  year      = {2013},
  abstract  = {At z < 1 a large fraction of the baryons is thought to reside in diffuse gas that has been shock-heated to high temperatures (10 (5)-10 (6) K). Absorption by the 770.41, 780.32 A doublet of Ne viii in quasar spectra represents a unique tool to study this elusive warm-hot phase. We have developed an analytic model for the properties of Ne viii absorbers that allows for an inhomogeneous metal distribution. Our model agrees with the predictions of a simulation from the OverWhelmingly Large Simulations project indicating that the average line-of-sight metal-filling fraction within the absorbing gas is low (c(L) similar to 0.1). Most of the Ne viii in our model is produced in low-density, collisionally ionized gas (n(H) = 10(-6)-10(-4) cm(-3), T = 10 (5)-10 (6) K). Strong Ne viii absorbers (log(10)(N-NeVIII/cm(-2))14), like those recently detected by Hubble Space Telescope/Cosmic Origins Spectrograph, are found to arise in higher density gas (n(H) greater than or similar to 10(-4) cm(-3), T approximate to 5 x 10 (5) K). Ne viii 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 Ne viii cloudlets) is a factor c(-1)L higher. We conclude that Ne viii 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.},
  language  = {en}
}
@article{TepperGarciaRichterSchayeetal.2011,
  author    = {Tepper-Garcia, Thorsten and Richter, Philipp and Schaye, Joop and Booth, C. M. and Vecchia, Claudio Dalla and Theuns, Tom and Wiersma, Robert P. C.},
  title     = {Absorption signatures of warm-hot gas at low redshift o vi},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {413},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {1},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2010.18123.x},
  pages     = {190 -- 212},
  year      = {2011},
  abstract  = {We investigate the origin and physical properties of O vi absorbers at low redshift (z = 0.25) using a subset of cosmological, hydrodynamical simulations from the OverWhelmingly Large Simulations (OWLS) project. Intervening O vi absorbers are believed to trace shock-heated gas in the warm-hot intergalactic medium (WHIM) and may thus play a key role in the search for the missing baryons in the present-day Universe. When compared to observations, the predicted distributions of the different O vi line parameters (column density, Doppler parameter, rest equivalent width W-r) from our simulations exhibit a lack of strong O vi absorbers, a discrepancy that has also been found by Oppenheimer \& Dave. This suggests that physical processes on subgrid scales (e.g. turbulence) may strongly influence the observed properties of O vi systems. We find that the intervening O vi absorption arises mainly in highly metal enriched (10-1 < Z/Z(circle dot) less than or similar to 1) gas at typical overdensities of 1 < /<<>> less than or similar to 102. One-third of the O vi absorbers in our simulation are found to trace gas at temperatures T < 105 K, while the rest arises in gas at higher temperatures, most of them around T = 105.3 +/- 0.5 K. These temperatures are much higher than inferred by Oppenheimer \& Dave, probably because that work did not take the suppression of metal-line cooling by the photoionizing background radiation into account. While the O vi resides in a similar region of (, T)-space as much of the shock-heated baryonic matter, the vast majority of this gas has a lower metal content and does not give rise to detectable O vi absorption. As a consequence of the patchy metal distribution, O vi absorbers in our simulations trace only a very small fraction of the cosmic baryons (< 2 per cent) and the cosmic metals. Instead, these systems presumably trace previously shock-heated, metal-rich material from galactic winds that is now mixing with the ambient gas and cooling. The common approach of comparing O vi and H i column densities to estimate the physical conditions in intervening absorbers from QSO observations may be misleading, as most of the H i (and most of the gas mass) is not physically connected with the high-metallicity patches that give rise to the O vi absorption.},
  language  = {en}
}
@article{TepperGarciaRichterSchayeetal.2012,
  author    = {Tepper-Garcia, Thorsten and Richter, Philipp and Schaye, Joop and Booth, C. M. and Dalla Vecchia, Claudio and Theuns, Tom},
  title     = {Absorption signatures of warm-hot gas at low redshift: broad H?i Lya absorbers},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {425},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {3},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2012.21545.x},
  pages     = {1640 -- 1663},
  year      = {2012},
  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.},
  language  = {en}
}
@article{BoucheFinleySchroetteretal.2016,
  author    = {Bouche, Nicolas and Finley, H. and Schroetter, I. and Murphy, M. T. and Richter, Philipp and Bacon, Roland and Contini, Thierry and Richard, J. and Wendt, Martin and Kamann, S. and Epinat, Benoit and Cantalupo, Sebastiano and Straka, Lorrie A. and Schaye, Joop and Martin, C. L. and Peroux, C. and Wisotzki, Lutz and Soto, K. and Lilly, S. and Carollo, C. M. and Brinchmann, Jarle and Kollatschny, W.},
  title     = {POSSIBLE SIGNATURES OF A COLD-FLOW DISK FROM MUSE USING A z similar to 1 GALAXY-QUASAR PAIR TOWARD SDSS J1422-0001},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {820},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.3847/0004-637X/820/2/121},
  pages     = {1872 -- 1882},
  year      = {2016},
  abstract  = {We use a background quasar to detect the presence of circumgalactic gas around a z = 0.91 low-mass star-forming galaxy. Data from the new Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope show that the galaxy has a dust-corrected star formation rate (SFR) of 4.7 +/- 2.0. M-circle dot yr(-1), with no companion down to 0.22 M-circle dot yr(-1) (5 sigma) within 240 h(-1) kpc ("30"). Using a high-resolution spectrum of the background quasar, which is fortuitously aligned with the galaxy major axis (with an azimuth angle alpha of only 15 degrees), we find, in the gas kinematics traced by low-ionization lines, distinct signatures consistent with those expected for a "cold-flow disk" extending at least 12 kpc (3 x R-1/2). We estimate the mass accretion rate M-in to be at least two to three times larger than the SFR, using the geometric constraints from the IFU data and the H (I) column density of log N-H (I)/cm(-2) similar or equal to 20.4 obtained from a Hubble Space Telescope/COS near-UV spectrum. From a detailed analysis of the low-ionization lines (e.g., Zn II, Cr II, Ti II, MnII, Si II), the accreting material appears to be enriched to about 0.4 Z(circle dot) (albeit with large uncertainties: log Z/Z(circle dot) = -0.4 +/- 0.4), which is comparable to the galaxy metallicity (12 + log O/H = 8.7 +/- 0.2), implying a large recycling fraction from past outflows. Blueshifted Mg II and Fe II absorptions in the galaxy spectrum from the MUSE data reveal the presence of an outflow. The Mg II and Fe II absorption line ratios indicate emission infilling due to scattering processes, but the MUSE data do not show any signs of fluorescent Fe II* emission.},
  language  = {en}
}