Absorption-Line Probes of Gas and Dust in Galactic Superwinds

By T. Heckman, M. Lehnert, D. Strickland, Lee Armus. 2000

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We have obtained moderate resolution (R = few thousand) spectra of the Na I λλ5890, 5896 (Na D) absorption line in a sample of 32 far-IR-bright starburst galaxies. In 18 cases, the Na D line in the nucleus is produced primarily by interstellar gas, while cool stars contribute significantly in the others. In 12 of the 18 "interstellar-dominated" cases the Na D line is blueshifted by over 100 km s-1 relative to the galaxy systemic velocity (the "outflow sources"), while no case shows a net redshift of more than 100 km s-1. The absorption-line profiles in these outflow sources span the range from near the galaxy systemic velocity to a maximum blueshift of ∼400-600 km s-1. The outflow sources are galaxies systematically viewed more nearly face-on than the others. We therefore argue that the absorbing material consists of ambient interstellar material that has been entrained and accelerated along the minor axis of the galaxy by a hot starburst-driven superwind. The Na D lines are optically thick, but indirect arguments imply total hydrogen column densities of NH ∼ few × 1021 cm-2. This implies that the superwind is expelling matter at a rate comparable to the star formation rate. This outflowing material is evidently very dusty: we find a strong correlation between the depth of the Na D profile and the line-of-sight reddening. Typical implied values are E(B-V) = 0.3-1 over regions several-to-10 kpc in size. We briefly consider some of the potential implications of these observations. The estimated terminal velocities of superwinds inferred from the present data and extant X-ray data are typically 400-800 km-1, are independent of the galaxy rotation speed, and are comparable to (substantially exceed) the escape velocities for L* (dwarf) galaxies. The resulting selective loss of metals from shallower potential wells can establish the mass-metallicity relation in spheroids, produce the observed metallicity in the intracluster medium, and enrich a general IGM to of order 10-1 solar metallicity. If the outflowing dust grains can survive their journey into the IGM, their effect on observations of cosmologically distant objects would be significant.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3e1c0db2e2527ac451cb0ccf84a1f9c9a6b39498

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Citations in the corpus

Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population (2014, background): “These “mass loading” values are typically higher than those observed in star-forming galaxiesbut similar to those seen in luminous AGN, derived from a variety of observations of outflows in different gas phases (e.g., Martin1999; Heckman et al. 2000; Newman et al. 2012; Cicone et al. 2014).”
Mapping Large-Scale Gaseous Outflows in Ultraluminous Galaxies with Keck II ESI Spectra: Variations in Outflow Velocity with Galactic Mass (2004, methodology): “While turbulent motion, particularly at the interfaces between the hot wind and the disk (e.g. Figure 11 in Heckman et al. 2000), is expected to broaden the lines, numerical simulations of bipolar outflows appear to have difficulty producing the large observed velocity range (D. Strickland, pvt…”
Galaxies and Intergalactic Matter at Redshift z ~ 3: Overview (2002, background): “Strong winds with velocities exceeding the escape velocity have been observed around a large fraction of starburst galaxies in the local universe (e.g. Heckman et al. 2000).”
Outflows in Infrared-Luminous Starbursts at z < 0.5. I. Sample, Na I D Spectra, and Profile Fitting (2005, methodology): “We can estimate the expected stellar contribution to Na iD by scaling the equivalent width of the Mg i b triplet, kk5167, 5173, 5185 (Heckman et al. 2000; Rupke et al. 2002).”
RADIATION PRESSURE FROM MASSIVE STAR CLUSTERS AS A LAUNCHING MECHANISM FOR SUPER-GALACTIC WINDS (2010, background): “…velocities ranging from a few tens to several hundred kilometers per second (Heckman, Armus, & Miley 1990; Steidel et al. 1996; Franx et al. 1997; Heckman et al. 2000; Pettini et al. 2000, 2001; Shapley et al. 2003; Martin 2005; Rupke et al. 2005; Tremonti et al. 2007; Weiner et al. 2009; Ménard…”
Extreme Gas Kinematics in the z = 2.2 Powerful Radio Galaxy MRC 1138–262: Evidence for Efficient Active Galactic Nucleus Feedback in the Early Universe? (2006, background): “From low-redshift studies, starburst- driven ‘‘superwinds’’ are known to be efficient in driving out gas only from the comparably shallow gravitational potentials of low-mass galaxies (e.g., Martin 1999; Lehnert et al. 1999; Heckman et al. 2000).”
EVIDENCE FOR UBIQUITOUS COLLIMATED GALACTIC-SCALE OUTFLOWS ALONG THE STAR-FORMING SEQUENCE AT z ∼ 0.5 (2013, methodology): “…of winds around systems with extreme characteristics; i.e., exceptionally high spatial concentrations of star formation (ΣSFR & 0.1 M⊙ yr −1 kpc−2; Schwartz & Martin 2004; Tremonti et al. 2007; Diamond-Stanic et al. 2012) and/or ongoing merger activity (e.g., Heckman et al. 2000; Martin 2005).”
SDSS IV MaNGA – metallicity and nitrogen abundance gradients in local galaxies (2017, background): “Decades of observational work have now demonstrated the ubiquitous presence of galactic winds, affecting all phases of the interstellar medium (ISM, Heckman et al. 2000; Martin 2005; c© 2016 The Authors ar X iv :1 70 3.”
INTEGRAL FIELD SPECTROSCOPY OF MASSIVE, KILOPARSEC-SCALE OUTFLOWS IN THE INFRARED-LUMINOUS QSO Mrk 231 (2011, background): “ULIRGs host powerful starburst-driven outflows (Heckman et al. 1990, 2000) that arise in all ULIRGs (Rupke et al. 2005c) and show kpc scale extents (Martin 2006; Shih & Rupke 2010).”
The Dust Opacity of Star‐forming Galaxies (2001, background): “In addition, hotstar-winds- and supernova-driven outflows evacuate both interstellar gas and dust from the region (Heckman, Armus & Miley 1990; De Young & Heckman 1994; Mac Low & Ferrara 1999; Ferrara & Tolstoy 2000; Heckman et al. 2000).”
Cosmological smoothed particle hydrodynamics simulations: a hybrid multiphase model for star formation (2002, background): “…for the rich phenomenology associated with starbursts and galactic outflows, which are observed at both low (e.g. Heckman et al., 1995; BlandHawthorn, 1995; Lehnert & Heckman, 1996; Dahlem et al., 1997; Heckman et al., 2000) and high redshifts (e.g. Frye et al., 2002; Pettini et al., 2000, 2001).”
Galactic winds driven by cosmic ray streaming (2012, background): “Large mass loading factors (defined as massloss rate divided by the SFR) with values of a few are estimated for local galaxies and massive star-forming regions at z ∼ 2–3 (Martin 1999; Heckman et al. 2000; Sato et al. 2009; Steidel et al. 2010; Coil et al. 2011).”
Evidence for Solar Metallicities in Massive Star-forming Galaxies at z ≳ 2 (2004, background): “…the chemical evolution of galaxies and of the intergalactic medium (IGM) are interconnected processes, since feedback from star formation in galaxies may be responsible for polluting the IGM with heavy elements over a wide range of redshifts (Heckman et al. 2000; Adelberger et al. 2003).”
Constraints on star formation driven galaxy winds from the mass–metallicity relation at z= 0 (2010, background): “While many metals (oxygen, as well as, e.g., iron, sodium, carbon, magnesium, and neon; Heckman et al. 2000; Martin 2005; Strickland & Heckman 2007; Martin & Bouché 2009; Grimes et al. 2009; Spoon & Holt 2009) are observed in galaxy outflows, there are relatively few observations of outflowing…”
The history of star-forming galaxies in the Sloan Digital Sky Survey (2007, background): “In principle, this is a more precise procedure than estimating the stellar NaD from its relation to other stellar absorption lines (Heckman et al. 2000; Schwartz & Martin 2004), but since the NaD window was masked in all fits (precisely because of its possible contamination by ISM absorption), the…”