MusE GAs FLOw and Wind V. The dust/metallicity-anisotropy of the circum-galactic medium
02 Mar 2021-Monthly Notices of the Royal Astronomical Society (Oxford Academic)-Vol. 502, Iss: 3, pp 3733-3745
TL;DR: In this paper, the authors show that the CGM along the minor axis is on average more metal enriched than the gas located along the major axis of galaxies, consistent with outflow and accretion models.
Abstract: Based on 13 galaxy-MgII absorber pairs (9 - 81 kpc distance) from the MusE GAs FLOw and Wind (MEGAFLOW) survey at 0.4 0.8 along the minor axis. Given that [Zn/Fe] is a good proxy for metallicity, these results suggest that the CGM along the minor axis is on average more metal enriched (by ~ 1dex) than the gas located along the major axis of galaxies - consistent with outflow and accretion models. Our results suggest a metallicity anisotropy of the CGM provided there is a constant dust-to-metal ratio.
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01 Jan 1985
TL;DR: In this article, a reexamination is conducted of the formation of dwarf, diffuse, metal-poor galaxies due to supernova-driven winds, in view of data on the systematic properties of dwarfs in the Local Group and Virgo Cluster.
Abstract: A reexamination is conducted of the formation of dwarf, diffuse, metal-poor galaxies due to supernova-driven winds, in view of data on the systematic properties of dwarfs in the Local Group and Virgo Cluster. The critical condition for global gas loss as a result of the first burst of star formation is that the virial velocity lie below an approximately 100 km/sec critical value. This leads, as observed, to two distinct classes of galaxies, encompassing the diffuse dwarfs, which primarily originate from typical density perturbations, and the normal, brighter galaxies, including compact dwarfs, which can originate only from the highest density peaks. This furnishes a statistical biasing mechanism for the preferential formation of bright galaxies in denser regions, enhancing high surface brightness galaxies' clustering relative to the diffusive dwarfs.
1,253 citations
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01 Jan 2000
74 citations
University of Saint Mary1, École normale supérieure de Lyon2, Leibniz Institute for Astrophysics Potsdam3, Leiden University4, University of Geneva5, University of Potsdam6, Paris Diderot University7, University of Toulouse8, Inter-University Centre for Astronomy and Astrophysics9, ETH Zurich10, University of Milan11, University of Porto12
TL;DR: In this paper, the first detection of extended MgII emission from a galaxy's halo that is probed by a quasar sightline was reported using deep (11.2hr) VLT/MUSE data from the MEGAFLOW survey.
Abstract: Using deep (11.2hr) VLT/MUSE data from the MEGAFLOW survey, we report the first detection of extended MgII emission from a galaxy's halo that is probed by a quasar sightline. The MgII $\lambda\lambda$ 2796,2803 emission around the $z = 0.702$ galaxy ($\log(M_*/\mathrm{M_\odot}) = 10.05^{+0.15}_{-0.11}$) is detected out to $\approx$25 kpc from the central galaxy and covers $1.0\times10^3$ kpc$^2$ above a surface brightness of $14\times10^{-19} \mathrm{erg} \mathrm{s}^{-1} \mathrm{cm}^{-2}\,\mathrm{arcsec}^{-2}$ ($2 \sigma$; integrated over 1200 km s$^{-1}$ =19A and averaged over $1.5 \;\mathrm{arcsec}^2$). The MgII emission around this highly inclined galaxy ($\simeq$75 deg) is strongest along the galaxy's projected minor axis, consistent with the MgII gas having been ejected from the galaxy into a bi-conical structure. The quasar sightline, which is aligned with the galaxy's minor axis, shows strong MgII $\lambda$2796 absorption (EW$_0$ = 1.8A) at an impact parameter of 39kpc from the galaxy. Comparing the kinematics of both the emission and the absorption - probed with VLT/UVES -, to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow ($v_\mathrm{out}= 130\;\mathrm{km}\,\mathrm{s}^{-1}$). We investigate potential origins of the extended MgII emission using simple toy models. With continuum scattering models we encounter serious difficulties in explaining the luminosity of the MgII halo and in reconciling density estimates from emission and absorption. Instead, we find that shocks might be a more viable source to power the extended MgII (and non-resonant [OII]) emission.
27 citations
TL;DR: In this paper, the dust-corrected metallicity of the neutral ISM measured towards 25 stars in our Galaxy was investigated and the results suggest that this low-metallicity accreting gas does not efficiently mix into the ISM.
Abstract: The Interstellar Medium (ISM) comprises gases at different temperatures and densities, including ionized, atomic, molecular species, and dust particles. The neutral ISM is dominated by neutral hydrogen and has ionization fractions up to 8%. The concentration of chemical elements heavier than helium (metallicity) spans orders of magnitudes in Galactic stars, because they formed at different times. Instead, the gas in the Solar vicinity is assumed to be well mixed and have Solar metallicity in traditional chemical evolution models. The ISM chemical abundances can be accurately measured with UV absorption-line spectroscopy. However, the effects of dust depletion, which removes part of the metals from the observable gaseous phase and incorporates it into solid grains, have prevented, until recently, a deeper investigation of the ISM metallicity. Here we report the dust-corrected metallicity of the neutral ISM measured towards 25 stars in our Galaxy. We find large variations in metallicity over a factor of 10 (with an average 55 +/- 7% Solar and standard deviation 0.28 dex) and including many regions of low metallicity, down to ~17% Solar and possibly below. Pristine gas falling onto the disk in the form of high-velocity clouds can cause the observed chemical inhomogeneities on scales of tens of pc. Our results suggest that this low-metallicity accreting gas does not efficiently mix into the ISM, which may help us understand metallicity deviations in nearby coeval stars.
27 citations
TL;DR: In this article, Keck/ESI spectra of nine gravitationally lensed z = 2-3 star forming galaxies were used to investigate the chemical composition and mass loss rate of outflows.
Abstract: Galactic-scale outflows regulate the stellar mass growth and chemical enrichment of galaxies, yet key outflow properties such as the chemical composition and mass loss rate remain largely unknown. We address these properties with Keck/ESI echellete spectra of nine gravitationally lensed z=2-3 star forming galaxies, probing a range of absorption transitions. Interstellar absorption in our sample is dominated by outflowing material, with typical velocities -150 km/s. Approximately 80% of the total column density is associated with a net outflow. Mass loss rates in the low ionization phase are comparable to or in excess of the star formation rate, with total outflow rates likely higher when accounting for ionized gas. Of order half of the heavy element yield from star formation is ejected in the low ionization phase, confirming that outflows play a critical role in regulating galaxy chemical evolution. Covering fractions vary and are in general non-uniform, with most galaxies having incomplete covering by the low ions across all velocities. Low ion abundance patterns show remarkably little scatter, revealing a distinct "chemical fingerprint" of outflows. Gas phase Si/Fe abundances are significantly super-solar ([Si/Fe]$\gtrsim$0.4) indicating a combination of $\alpha$-enhancement and dust depletion. Derived properties are comparable to the most kinematically broad, metal-rich, and depleted intergalactic absorption systems at similar redshifts, suggesting that these extreme systems are associated with galactic outflows at impact parameters conservatively within a few tens of kpc. We discuss implications of the abundance patterns in z=2-3 galaxies and the role of outflows at this epoch.
24 citations
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TL;DR: Matplotlib is a 2D graphics package used for Python for application development, interactive scripting, and publication-quality image generation across user interfaces and operating systems.
Abstract: Matplotlib is a 2D graphics package used for Python for application development, interactive scripting,and publication-quality image generation across user interfaces and operating systems
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"MusE GAs FLOw and Wind V. The dust/..." refers methods in this paper
...This work made use of the following open source software: GalPaK3D (Bouché et al. 2015), ZAP (Soto et al. 2016), MPDAF (Piqueras et al. 2017), matplotlib (Hunter 2007), NumPy (van der Walt et al. 2011; Oliphant 2007), Astropy (Astropy Collaboration et al. 2013), especia (Quast 2016)....
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"MusE GAs FLOw and Wind V. The dust/..." refers methods in this paper
...This work made use of the following open source software: GalPaK3D (Bouché et al. 2015), ZAP (Soto et al. 2016), MPDAF (Piqueras et al. 2017), matplotlib (Hunter 2007), NumPy (van der Walt et al. 2011; Oliphant 2007), Astropy (Astropy Collaboration et al. 2013), especia (Quast 2016)....
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