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Register a new userThe spatially-resolved gas and dust connection in neutral inflows and outflows in nearby AGN
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David S. N. Rupke
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Dusty, neutral outflows and inflows are a common feature of nearby star-forming galaxies. We characterize these flows in eight galaxies -- mostly AGN -- selected for their widespread NaI D signatures from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). This survey employs deep, wide field-of-view integral field spectroscopy at moderate spectral resolution (R=7000 at NaI D). We significantly expand the sample of sightlines in external galaxies in which the spatially-resolved relationship has been studied between cool, neutral gas properties -- N(NaI), Weq(NaI D) -- and dust -- E(B-V) from both stars and gas. Our sample shows strong, significant correlations of total Weq with E(B-V)_stars and g-i colour within individual galaxies; correlations with E(B-V)_gas are present but weaker. Regressions yield slope variations from galaxy to galaxy and intrinsic scatter ~1 Angstrom. The sample occupies regions in the space of N(NaI) and Weq^abs vs. E(B-V)_gas that are consistent with extrapolations from other studies to higher colour excess [E(B-V)_gas ~ 1]. For perhaps the first time in external galaxies, we detect inverse P Cygni profiles in the NaI D line, presumably due to inflowing gas. Via Doppler shifted NaI D absorption and emission lines, we find ubiquitous flows that differ from stellar rotation by >100 km/s or have |v,abs - v,em| > 100 km/s. Inflows and outflows extend toward the edge of the detected stellar disk/FOV, together subtend 10-40% of the projected disk, and have similar mean N(NaI) and Weq(NaI D). Outflows are consistent with minor-axis or jet-driven flows, while inflows tend toward the projected major axis. The inflows may result from non-axisymmetric potentials, tidal motions, or halo infall.
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We perform a stacking analysis of the neutral ad,$lambdalambda$5889,5895,AA ISM doublet using the SDSS DR7 spectroscopic data set to probe the prevalence and characteristics of cold (T,$lesssim$,10$^{4}$,K) galactic-scale gas flows in local (0.025$leqslant zleqslant$0.1) inactive and AGN-host galaxies across the SFR-M$_{*}$ plane. We find low-velocity outflows to be prevalent in regions of high SFRs and stellar masses (10 $lesssim$log M$_{*}$/M$_{odot}$ $lesssim$ 11.5), however we do not find any detections in the low mass (log M$_{*}$/M$_{odot}$ $lesssim$ 10) regime. We also find tentative detections of inflowing gas in high mass galaxies across the star-forming population. We derive mass outflow rates in the range of 0.14-1.74,M$_{odot}$yr$^{-1}$ and upper limits on inflow rates <1,M$_{odot}$yr$^{-1}$, allowing us to place constraints on the mass loading factor ($eta$=$dot{M}_{text{out}}$/SFR) for use in simulations of the local Universe. We discuss the fate of the outflows by comparing the force provided by the starburst to the critical force needed to push the outflow outward, and find the vast majority of the outflows unlikely to escape the host system. Finally, as outflow detection rates and central velocities do not vary strongly with the presence of a (weak) active supermassive black hole, we determine that star formation appears to be the primary driver of outflows at $zsim$0.
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