New Perspective on Galaxy Outflows From the First Detection of Both Intrinsic and Traverse Metal-Line Absorption
TL;DR: In this paper, the first observation of a galaxy (z=0.2) that exhibits metal-line absorption back-illuminated by the galaxy ("down-the-barrel") and transversely by a background quasar at a projected distance of 58 kpc.
Abstract: We present the first observation of a galaxy (z=0.2) that exhibits metal-line absorption back-illuminated by the galaxy ("down-the-barrel") and transversely by a background quasar at a projected distance of 58 kpc. Both absorption systems, traced by MgII, are blueshifted relative to the galaxy systemic velocity. The quasar sight-line, which resides almost directly along the projected minor axis of the galaxy, probes MgI and MgII absorption obtained from Keck/LRIS and Lya, SiII and SiIII absorption obtained from HST/COS. For the first time, we combine two independent models used to quantify the outflow properties for down-the-barrel and transverse absorption. We find that the modeled down-the-barrel deprojected outflow velocities range between $V_{dtb}=45-255$ km/s. The transverse bi-conical outflow model, assuming constant-velocity flows perpendicular to the disk, requires wind velocities $V_{outflow}=40-80$ km/s to reproduce the transverse MgII absorption kinematics, which is consistent with the range of $V_{dtb}$. The galaxy has a metallicity, derived from H$\alpha$ and NII, of $[{\rm O/H}]=-0.21\pm0.08$, whereas the transverse absorption has $[{\rm X/H}]=-1.12\pm0.02$. The galaxy star-formation rate is constrained between $4.6-15$ M$_{\odot}$/yr while the estimated outflow rate ranges between $1.6-4.2$ M$_{\odot}$/yr and yields a wind loading factor ranging between $0.1-0.9$. The galaxy and gas metallicities, the galaxy-quasar sight-line geometry, and the down-the-barrel and transverse modeled outflow velocities collectively suggest that the transverse gas originates from ongoing outflowing material from the galaxy. The $\sim$1 dex decrease in metallicity from the base of the outflow to the outer halo suggests metal dilution of the gas by the time it reached 58 kpc.
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TL;DR: In this paper, the presence of an extended and massive circumgalactic medium (CGM) around Messier 31 using archival HST Cosmic Origins Spectrograph ultraviolet spectroscopy of 18 QSOs projected within two virial radii of M31 (kpc).
Abstract: We demonstrate the presence of an extended and massive circumgalactic medium (CGM) around Messier 31 using archival HST Cosmic Origins Spectrograph ultraviolet spectroscopy of 18 QSOs projected within two virial radii of M31 ( kpc). We detect absorption from Si iii at km s−1 toward all three sightlines at , 3 of 4 sightlines at , and possibly 1 of 11 at . We present several arguments that the gas at these velocities observed in these directions originates from the M31 CGM rather than the Local Group or Milky Way CGM or Magellanic Stream. We show that the dwarf galaxies located in the CGM of M31 have very similar velocities over similar projected distances from M31. We find a non-trivial relationship only at these velocities between the column densities (N) of all the ions and R, whereby N decreases with increasing R. At , the covering fraction is close to unity for Si iii and C iv (–97% at the 90% confidence level), but drops to –20% at . We show that the M31 CGM gas is bound, multiphase, predominantly ionized, and is more highly ionized gas at larger R. We estimate using Si ii, Si iii, and Si iv, a CGM metal mass of M and gas mass of M within , and possibly a factor of ∼10 larger within , implying substantial metal and gas masses in the CGM of M31.
151 citations
TL;DR: In this paper, an analysis of the flow of metals through the circumgalactic medium (CGM) in the Feedback in Realistic Environments (FIRE) simulations of galaxy formation, ranging from isolated dwarfs to L* galaxies, is presented.
Abstract: We present an analysis of the flow of metals through the circumgalactic medium (CGM) in the Feedback in Realistic Environments (FIRE) simulations of galaxy formation, ranging from isolated dwarfs to L* galaxies. We find that nearly all metals produced in high-redshift galaxies are carried out in winds that reach 0.25R_(vir). When measured at 0.25R_(vir) the metallicity of outflows is slightly higher than the interstellar medium (ISM) metallicity. Many metals thus reside in the CGM. Cooling and recycling from this reservoir determine the metal budget in the ISM. The outflowing metal flux decreases by a factor of ∼2–5 between 0.25R_(vir) and R_(vir). Furthermore, outflow metallicity is typically lower at R_(vir) owing to dilution of the remaining outflow by metal-poor material swept up from the CGM. The inflow metallicity at R_(vir) is generally low, but outflow and inflow metallicities are similar in the inner halo. At low redshift, massive galaxies no longer generate outflows that reach the CGM, causing a divergence in CGM and ISM metallicity. Dwarf galaxies continue to generate outflows, although they preferentially retain metal ejecta. In all but the least massive galaxy considered, a majority of the metals are within the halo at z = 0. We measure the fraction of metals in CGM, ISM and stars, and quantify the thermal state of CGM metals in each halo. The total amount of metals in the low-redshift CGM of two simulated L* galaxies is consistent with estimates from the Cosmic Origin Spectrograph haloes survey, while for the other two it appears to be lower.
140 citations
Cites background from "New Perspective on Galaxy Outflows ..."
...Some of the best constraints on galactic wind outflow rates come from instances where a quasar line-of-sight aligns with the minor axis of a star-forming galaxy (Bouché et al. 2012; Kacprzak et al. 2014; Schroetter et al. 2015)....
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TL;DR: In this article, a Markov Chain Monte Carlo (MCMC) approach is used to constrain the kinematics and morphological parameters of a galaxy in non-merging conditions, provided that the maximum signal-to-noise ratio (S/N) is greater than ∼3 pixel−1 and the ratio of galaxy half-light radius to seeing radius is more than 1.5.
Abstract: We present a method to constrain galaxy parameters directly from three-dimensional data cubes. The algorithm compares directly the data with a parametric model mapped in coordinates. It uses the spectral line-spread function and the spatial point-spread function (PSF) to generate a three-dimensional kernel whose characteristics are instrument specific or user generated. The algorithm returns the intrinsic modeled properties along with both an “intrinsic” model data cube and the modeled galaxy convolved with the 3D kernel. The algorithm uses a Markov Chain Monte Carlo approach with a nontraditional proposal distribution in order to efficiently probe the parameter space. We demonstrate the robustness of the algorithm using 1728 mock galaxies and galaxies generated from hydrodynamical simulations in various seeing conditions from 0.″6 to 1.″2. We find that the algorithm can recover the morphological parameters (inclination, position angle) to within 10% and the kinematic parameters (maximum rotation velocity) to within 20%, irrespectively of the PSF in seeing (up to 1.″2) provided that the maximum signal-to-noise ratio (S/N) is greater than ∼3 pixel−1 and that the ratio of galaxy half-light radius to seeing radius is greater than about 1.5. One can use such an algorithm to constrain simultaneously the kinematics and morphological parameters of (nonmerging) galaxies observed in nonoptimal seeing conditions. The algorithm can also be used on adaptive optics data or on high-quality, high-S/N data to look for nonaxisymmetric structures in the residuals.
111 citations
Hoffmann-La Roche1, Centre national de la recherche scientifique2, Swinburne University of Technology3, University of Potsdam4, Leibniz Institute for Astrophysics Potsdam5, École normale supérieure de Lyon6, University of Göttingen7, Aix-Marseille University8, ETH Zurich9, Leiden University10, University of California, Santa Barbara11, University of Porto12
TL;DR: Bouche et al. as discussed by the authors used a background quasar to detect the presence of circumgalactic gas around a z = 0.91 low-mass star-forming galaxy.
Abstract: Author(s): Bouche, N; Finley, H; Schroetter, I; Murphy, MT; Richter, P; Bacon, R; Contini, T; Richard, J; Wendt, M; Kamann, S; Epinat, B; Cantalupo, S; Straka, LA; Schaye, J; Martin, CL; Peroux, C; Wisotzki, L; Soto, K; Lilly, S; Carollo, CM; Brinchmann, J; Kollatschny, W | 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⊙ yr-1, with no companion down to 0.22 M⊙ yr-1 (5σ) 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 α of only 15°), 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 × R1/2). We estimate the mass accretion rate Ṁin 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 NH I/cm-2 ≃ 20.4 obtained from a Hubble Space Telescope/COS near-UV spectrum. From a detailed analysis of the lowionization lines (e.g., Zn II, Cr II, Ti II, Mn II, Si II), the accreting material appears to be enriched to about 0.4 Z⊙ (albeit with large uncertainties: log Z/Z⊙ = -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.
106 citations
Cites background or methods from "New Perspective on Galaxy Outflows ..."
...Such analyses are powerful, but have only been possible in very few cases, such as in Steidel et al. (2002), Bouché et al. (2012, 2013), Kacprzak et al. (2010, 2014),and Schroetter et al. (2015) with background quasars and in Rubin et al. (2010) and Diamond-Stanic et al. (2015) with a bright…...
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...Hence, performing a double-Gaussian fit to the absorption representing the ISM18 and the wind components (as in Martin et al. 2012; Kacprzak et al. 2014) shown in Figure 4, we find that the wind speed (at peak optical depth) is about » -...
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...Furthermore, a simple bi-conical flow model—which has been successful in reproducing absorption profiles in Bouché et al. (2012), Kacprzak et al. (2014), and Schroetter et al. (2015)—would produce absorption at a single speed because the line of sight is almost entirely radial, and thus it would…...
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TL;DR: The stellar-to-halo mass relation (SHMR) as discussed by the authors is nearly time-independent for $z 4$ assuming that the interstellar gas mass is constant for each galaxy (the "equilibrium condition" in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas.
Abstract: The galaxy stellar-to-halo mass relation (SHMR) is nearly time-independent for $z 4$. Assuming that the interstellar gas mass is constant for each galaxy (the "equilibrium condition" in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas. With assumptions about preventive feedback based on simulations, SHARC allows calculation of galaxy metallicity evolution. If galaxy SFRs indeed track halo MARs, especially at low redshifts, that may help explain the success of models linking galaxy properties to halos (including age-matching) and the similarities between two-halo galaxy conformity and halo mass accretion conformity.
91 citations
Cites methods from "New Perspective on Galaxy Outflows ..."
...For comparison we include observational constraints on the mass loading factors from Bouché et al. (2012) for a sample at z ∼ 0.1, Kacprzak et al. (2014) for a galaxy sample at z ∼ 0.2 and Schroetter et al. (2015) for galaxies at z ∼ 0.8....
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References
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TL;DR: In this article, the authors focus on the broad patterns in the star formation properties of galaxies along the Hubble sequence and their implications for understanding galaxy evolution and the physical processes that drive the evolution.
Abstract: Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence and are key probes of the evolutionary histories of galaxies. The focus of this review is on the broad patterns in the star formation properties of galaxies along the Hubble sequence and their implications for understanding galaxy evolution and the physical processes that drive the evolution. Star formation in the disks and nuclear regions of galaxies are reviewed separately, then discussed within a common interpretive framework. The diagnostic methods used to measure SFRs are also reviewed, and a self-consistent set of SFR calibrations is presented as an aid to workers in the field. One of the most recognizable features of galaxies along the Hubble sequence is the wide range in young stellar content and star formation activity. This variation in stellar content is part of the basis of the Hubble classification itself (Hubble 1926), and understanding its physical nature and origins is fundamental to understanding galaxy evolution in its broader context. This review deals with the global star formation properties of galaxies, the systematics of those properties along the Hubble sequence, and their implications for galactic evolution. I interpret “Hubble sequence” in this context very loosely, to encompass not only morphological type but other properties such as gas content, mass, bar structure, and dynamical environment, which can strongly influence the largescale star formation rate (SFR).
6,640 citations
TL;DR: The Low Resolution Imaging Spectrometer (LRIS) for the Cassegrain focus of the Keck 10-meter telescope on Mauna Kea is described in this paper, which has an imaging mode so it can also be used for taking direct images.
Abstract: The Low Resolution Imaging Spectrometer (LRIS) for the Cassegrain focus of the Keck 10-meter telescope on Mauna Kea is described. It has an imaging mode so it can also be used for taking direct images. The field of view in both spectrographic and imaging modes is 6 by 7.8 arcmin. It can be used with both conventional slits and custom-punched slit masks. The optical quality of the spectrograph is good enough to take full advantage of the excellent imaging properties of the telescope itself. The detector is a cooled back-illuminated Tektronics Inc. 2048 CCD which gives a sampling rate of 4.685 pixels per arcsec. In the spectrographic mode the spectrograph has a maximum efficiency at the peak of the grating blaze of 32-34% for the two lowest resolution gratings and 28% for the 1200 g/mm grating. This efficiency includes the detector but not the telescope or the atmosphere.
2,237 citations
"New Perspective on Galaxy Outflows ..." refers methods in this paper
...The galaxy and background quasar spectra were obtained on 2013 April 11 using the Keck Low Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) with the blue 1200 lines mm−1 grism blazed at 3400 Å providing wavelength coverage from the atmospheric cut-off to 3890 Å....
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TL;DR: In this paper, the use of the ratio of nebular lines of [O III] and [N II], first introduced by Alloin et al., is reappraised with modern calibration data and shown to have certain advantages over Ρ 23 ≡ ([On] + [OIII])/Hβ and N2 ≡ [N 2] λ6583/Hα, particularly when applied to star-forming galaxies at high redshifts.
Abstract: Among 'empirical' methods of estimating oxygen abundances in extragalactic H II regions, the use of the ratio of nebular lines of [O III] and [N II], first introduced by Alloin et al., is reappraised with modern calibration data and shown to have certain advantages over Ρ 23 ≡ ([On] + [O III])/Hβ and N2 ≡ [N II] λ6583/Hα, particularly when applied to star-forming galaxies at high redshifts.
1,850 citations
"New Perspective on Galaxy Outflows ..." refers methods in this paper
...We apply the N2 metallicity relation 12 + log [O/H] = 8.90+0.57× N2 (Pettini & Pagel 2004), assuming a solar oxygen abundance of 12 + log [O/H] = 8.736 ± 0.078 (Holweger 2001), and compute a galaxy metallicity of [O/H] = −0.21 ± 0.08....
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TL;DR: In this article, the authors presented improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending their previous results, and provided tables of predicted H I and He II photoionization and photoheating rates for use, e.g., in cosmological hydrodynamics simulations of the Lyα forest and a new metallicity-dependent calibration to the UV luminosity density-star formation rate density relation.
Abstract: We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending our previous results. Five new main components are added to our radiative transfer code CUBA: (1) the sawtooth modulation of the background intensity from resonant line absorption in the Lyman series of cosmic hydrogen and helium; (2) the X-ray emission from the obscured and unobscured quasars that gives origin to the X-ray background; (3) a piecewise parameterization of the distribution in redshift and column density of intergalactic absorbers that fits recent measurements of the mean free path of 1 ryd photons; (4) an accurate treatment of the photoionization structure of absorbers, which enters in the calculation of the helium continuum opacity and recombination emissivity; and (5) the UV emission from star-forming galaxies at all redshifts. We provide tables of the predicted H I and He II photoionization and photoheating rates for use, e.g., in cosmological hydrodynamics simulations of the Lyα forest and a new metallicity-dependent calibration to the UV luminosity density-star formation rate density relation. A "minimal cosmic reionization model" is also presented in which the galaxy UV emissivity traces recent determinations of the cosmic history of star formation, the luminosity-weighted escape fraction of hydrogen-ionizing radiation increases rapidly with look-back time, the clumping factor of the high-redshift intergalactic medium evolves following the results of hydrodynamic simulations, and Population III stars and miniquasars make a negligible contribution to the metagalactic flux. The model provides a good fit to the hydrogen-ionization rates inferred from flux decrement and proximity effect measurements, predicts that cosmological H II (He III) regions overlap at redshift 6.7 (2.8), and yields an optical depth to Thomson scattering, τes = 0.084 that is in agreement with Wilkinson Microwave Anisotropy Probe results. Our new background intensities and spectra are sensitive to a number of poorly determined input parameters and suffer from various degeneracies. Their predictive power should be constantly tested against new observations. We are therefore making our redshift-dependent UV/X emissivities and CUBA outputs freely available for public use at http://www.ucolick.org/~pmadau/CUBA.
1,010 citations
"New Perspective on Galaxy Outflows ..." refers methods in this paper
...We apply the standard assumption that the (A color version of this figure is available in the online journal.) gas is represented by a photoionized uniform slab in ionization equilibrium illuminated with a Haardt & Madau (2012) ionizing spectrum....
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TL;DR: In this paper, a code CIGALE (Code Investigating GALaxy Emission) that uses model spectra composed of the Maraston (or PEGASE) stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, the Dale & Helou dust emission models, and optional spectral templates of obscured AGN is presented.
Abstract: Aims. Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make it possible to derive galaxy properties with a high reliability by fitting the attenuated stellar emission and the related dust emission at the same time.Methods. For this purpose we wrote the code CIGALE (Code Investigating GALaxy Emission) that uses model spectra composed of the Maraston (or PEGASE) stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, the Dale & Helou dust emission models, and optional spectral templates of obscured AGN. Depending on the input redshifts, filter fluxes were computed for the model set and compared to the galaxy photometry by carrying out a Bayesian-like analysis. CIGALE was tested by analysing 39 nearby galaxies selected from SINGS. The reliability of the different model parameters was evaluated by studying the resulting expectation values and their standard deviations in relation to the input model grid. Moreover, the influence of the filter set and the quality of photometric data on the code results was estimated.Results. For up to 17 filters with effective wavelengths between 0.15 and 160 μ m, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 A, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. Details of the star formation history (excepting the burst fraction) and the shape of the attenuation curve are difficult to investigate with the available broad-band UV and optical photometric data. A study of the mutual relations between the reliable properties confirms the dependence of star formation activity on morphology in the local Universe and indicates a significant drop in this activity at about 1011 towards higher total stellar masses. The dustiest galaxies in the SINGS sample are present in the same mass range. On the other hand, the far-UV attenuation of our sample galaxies does not appear to show a significant dependence on star formation activity.Conclusions. The results for our SINGS test sample demonstrate that CIGALE can be a valuable tool for studying basic properties of galaxies in the near and distant Universe if UV-to-IR data are available.
782 citations