Kiloparsec Scale Properties of Star Formation Driven Outflows at z ∼ 2.3 in the SINS/zC-SINF AO Survey*

Abstract

We investigate the relationship between star formation activity and outflow properties on kiloparsec scales in a sample of 28 star forming galaxies at z ∼ 2 -2.6, using adaptive optics assisted integral field observations from SINFONI on the VLT. The narrow and broad components of the Hα emission are used to simultaneously determine the local star formation rate surface density (Σ SFR ), and the outflow velocity v out and mass outflow rateṀ out , respectively. We find clear evidence for faster outflows with larger mass loading factors at higher Σ SFR . The outflow velocities scale as v out ∝ Σ SFR 0.34±0.10 , which suggests that the outflows may be driven by a combination of mechanical energy released by supernova explosions and stellar winds, as well as radiation pressure acting on dust grains. The majority of the outflowing material does not have sufficient velocity to escape from the galaxy halos, but will likely be re-accreted and contribute to the chemical enrichment of the galaxies. In the highest Σ SFR regions the outflow component contains an average of ∼45% of the Hα flux, while in the lower Σ SFR regions only ∼10% of the Hα flux is associated with outflows. The mass loading factor, η =Ṁ out /SFR, is positively correlated with Σ SFR but is relatively low even at the highest Σ SFR : η 0.5 × (380 cm −3 /n e ). This may be in tension with the η 1 required by cosmological simulations, unless a significant fraction of the outflowing mass is in other gas phases and has sufficient velocity to escape the galaxy halos.

Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

“…It is interesting to note that the physical properties derived for the outflow in J 1429 are quantitatively similar to that obtained by Davies et al (2019) (see also Newman et al 2012) following the same model prescriptions for starforming galaxies at z ∼ 2 after stacking AO-assisted IFU spectra (their Table 2). In Davies et al (2019), the outflows are resolved at kpc-scales in 11 out of 14 galaxies at z = 2.2 with stellar masses M * 10 10 M , which are located above the star formation main sequence and contribute to stacks with higher SFR/Area. These stacks are those showing higher broad-to-narrow emission ratio and outflow parameters closer to the values obtained for J 1429.…”

“…In order to further compare our results with those of star-forming galaxies at z ∼2 from long-slit and IFU spectroscopic surveys (e.g. Freeman et al 2019;Newman et al 2012;Davies et al 2019), we adopt an outflow model from Genzel et al (2011). This model assumes an spherically symmetric outflow with a constant velocity and an outflow rate defined as,…”

“…Star-formation driven outflows, seen in emission as low surface brightness broad components, are typically associated with a younger and denser phase of the superwind, which can extent out to kpc distances from the launching point (e.g. Genzel et al 2011;Newman et al 2012;Davies et al 2019). In contrast, more diffuse outflowing material expelled at usually larger spatial scales and over longer timescales can be detected as blueshifted absorptions in rest-frame UV spectra of star-forming galaxies at low and intermediate redshifts (e.g.…”

“…Castañeda et al 1990;Roy et al 1992;Martin 1998;Izotov et al 2007;James et al 2009;Firpo et al 2010Firpo et al , 2011Hägele et al 2012;Terlevich et al 2014;Arribas et al 2014;Lagos et al 2014;Rodríguez del Pino et al 2019) and higher redshift (e.g. Genzel et al 2011;Newman et al 2012;Freeman et al 2019;Davies et al 2019) has typically been ascribed to star-formation driven gas outflows. However, this may not always be the cause of broad component emission and other effects are not simple to disentangle.…”

Dust, Gas, and Metal Content in Star-forming Galaxies at z ∼ 3.3 Revealed with ALMA and Near-IR Spectroscopy

“…Direct measurements of gas outflow and inflow rates would be also important to further investigate whether the star-forming galaxies at z ∼ 3.3 are out of equilibrium. The spatially resolved emission line maps for the individual galaxies will enable us to search for outflow signatures and estimate the mass outflow rates (e.g., Genzel et al 2011;Davies et al 2019). Furthermore, a simulation study suggests a correlation between metallicity gradients and gas accretion rates (Collacchioni et al 2020).…”