Galaxy-scale outflows of gas, or galactic winds (GWs), driven by energy from star formation are a pivotal mechanism for regulation of star formation in the current model of galaxy evolution. ...Observations of this phenomenon have proliferated through the wide application of old techniques on large samples of galaxies, the development of new methods, and advances in telescopes and instrumentation. I review the diverse portfolio of direct observations of stellar GWs since 2010. Maturing measurements of the ionized and neutral gas properties of nearby winds have been joined by exciting new probes of molecular gas and dust. Low-z techniques have been newly applied in large numbers at high z. The explosion of optical and near-infrared 3D imaging spectroscopy has revealed the complex, multiphase structure of nearby GWs. These observations point to stellar GWs being a common feature of rapidly star-forming galaxies throughout at least the second half of cosmic history, and suggest that scaling relationships between outflow and galaxy properties persist over this period. The simple model of a modest-velocity, biconical flow of multiphase gas and dust perpendicular to galaxy disks continues to be a robust descriptor of these flows.
The quasi-stellar object (QSO)/merger Mrk 231 is arguably the nearest and best laboratory for studying QSO feedback. It hosts several outflows, including broad-line winds, radio jets, and a poorly ...understood kpc-scale outflow. In this Letter, we present integral field spectroscopy from the Gemini telescope that represents the first unambiguous detection of a wide-angle, kiloparsec-scale outflow from a powerful QSO. Using neutral gas absorption, we show that the nuclear region hosts an outflow with blueshifted velocities reaching 1100 km s--1, extending 2-3 kpc from the nucleus in all directions in the plane of the sky. A radio jet impacts the outflow north of the nucleus, accelerating it to even higher velocities (up to 1400 km s--1). Finally, 3.5 kpc south of the nucleus, star formation is simultaneously powering an outflow that reaches more modest velocities of only 570 km s--1. Blueshifted ionized gas is also detected around the nucleus at lower velocities and smaller scales. The mass and energy flux from the outflow are 2.5 times the star formation rate and 0.7% of the active galactic nucleus luminosity, consistent with negative feedback models of QSOs.
The prevalence and properties of kiloparsec-scale outflows in nearby Type 1 quasars have been the subject of little previous attention. This work presents Gemini integral field spectroscopy of 10 ...Type 1 radio-quiet quasars at . The excellent image quality, coupled with a new technique to remove the point-spread function using spectral information, allows the fitting of the underlying host on a spaxel-by-spaxel basis. Fits to stars, line-emitting gas, and interstellar absorption show that 100% of the sample hosts warm ionized and/or cool neutral outflows with spatially averaged velocities ( ) of 200-1300 and peak velocities (maximum ) of 500-2600 . These minor-axis outflows are powered primarily by the central active galactic nucleus, reach scales of 3-12 kpc, and often fill the field of view. Including molecular data and Type 2 quasar measurements, nearby quasars show a wide range in mass outflow rates ( to ) and momentum boosts . After extending the mass scale to Seyferts, dM/dt and dE/dt correlate with black hole mass ( and ). Thus, the most massive black holes in the local universe power the most massive and energetic quasar-mode winds.
We present metallicity gradients in 49 local field star-forming galaxies. We derive gas-phase oxygen abundances using two widely adopted metallicity calibrations based on the O iii/Hβ, N ii/Hα, and N ...ii/O ii line ratios. The two derived metallicity gradients are usually in good agreement within
$\pm 0.14\ {\rm dex} R_{25}^{-1}$
(
R
25 is the
B
-band iso-photoal radius), but the metallicity gradients can differ significantly when the ionization parameters change systematically with radius. We investigate the metallicity gradients as a function of stellar mass (
$8 {<} \log (M_\ast /M_\odot) {<} 11$
) and absolute
B
-band luminosity (−16 > M
B
> −22). When the metallicity gradients are expressed in dex kpc−1, we show that galaxies with lower mass and luminosity, on average, have steeper metallicity gradients. When the metallicity gradients are expressed in
${\rm dex} R_{25}^{-1}$
, we find no correlation between the metallicity gradients, and stellar mass and luminosity. We provide a local benchmark metallicity gradient of field star-forming galaxies useful for comparison with studies at high redshifts. We investigate the origin of the local benchmark gradient using simple chemical evolution models and observed gas and stellar surface density profiles in nearby field spiral galaxies. Our models suggest that the local benchmark gradient is a direct result of the coevolution of gas and stellar disc under virtually closed-box chemical evolution when the stellar-to-gas mass ratio becomes high (≫0.3). These models imply low current mass accretion rates ( ≲ 0.3 × SFR), and low-mass outflow rates ( ≲ 3 × SFR) in local field star-forming galaxies.
Massive, galaxy-scale outflows are known to be ubiquitous in major mergers of disk galaxies in the local universe. In this paper, we explore the multiphase structure and power sources of galactic ...winds in six ultra-luminous infrared galaxies (ULIRGs) at z < 0.06 using deep integral field spectroscopy with the Gemini Multi-Object Spectrograph (GMOS) on Gemini North. We probe the neutral, ionized, and dusty gas phases using Na i D, strong emission lines (OI, H alpha , and NII), and continuum colors, respectively. The properties of these outflows are consistent with multiphase (ionized, neutral, and dusty) collimated bipolar winds emerging along the minor axis of the nuclear disk to scales of 1-2 kpc. The outflow energy and momentum in the QSOs are difficult to produce from a star-burst alone, but are consistent with the QSO contributing significantly to the driving of the flow. Finally, when all gas phases are accounted for, the outflows are massive enough to provide negative feedback to star formation.
Ninety per cent of baryons are located outside galaxies, either in the circumgalactic or intergalactic medium
. Theory points to galactic winds as the primary source of the enriched and massive ...circumgalactic medium
. Winds from compact starbursts have been observed to flow to distances somewhat greater than ten kiloparsecs
, but the circumgalactic medium typically extends beyond a hundred kiloparsecs
. Here we report optical integral field observations of the massive but compact galaxy SDSS J211824.06+001729.4. The oxygen O II lines at wavelengths of 3726 and 3729 angstroms reveal an ionized outflow spanning 80 by 100 square kiloparsecs, depositing metal-enriched gas at 10,000 kelvin through an hourglass-shaped nebula that resembles an evacuated and limb-brightened bipolar bubble. We also observe neutral gas phases at temperatures of less than 10,000 kelvin reaching distances of 20 kiloparsecs and velocities of around 1,500 kilometres per second. This multi-phase outflow is probably driven by bursts of star formation, consistent with theory
.
We present
lzifu
(LaZy-IFU), an
idl
toolkit for fitting multiple emission lines simultaneously in integral field spectroscopy (IFS) data.
lzifu
is useful for the investigation of the dynamical, ...physical and chemical properties of gas in galaxies.
lzifu
has already been applied to many world-class IFS instruments and large IFS surveys, including the Wide Field Spectrograph, the new Multi Unit Spectroscopic Explorer (MUSE), the Calar Alto Legacy Integral Field Area (CALIFA) survey, the Sydney-Australian-astronomical-observatory Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. Here we describe in detail the structure of the toolkit, and how the line fluxes and flux uncertainties are determined, including the possibility of having multiple distinct kinematic components. We quantify the performance of
lzifu
, demonstrating its accuracy and robustness. We also show examples of applying
lzifu
to CALIFA and SAMI data to construct emission line and kinematic maps, and investigate complex, skewed line profiles presented in IFS data. The code is made available to the astronomy community through github.
lzifu
will be further developed over time to other IFS instruments, and to provide even more accurate line and uncertainty estimates.
ABSTRACT
Quasar-driven outflows must have made their most significant impact on galaxy formation during the epoch when massive galaxies were forming most rapidly. To study the impact of quasar ...feedback, we conducted rest-frame optical integral field spectrograph (IFS) observations of three extremely red quasars (ERQs) and one type-2 quasar at z = 2–3, obtained with the NIFS and OSIRIS instruments at the Gemini North and W. M. Keck Observatory with the assistance of laser-guided adaptive optics. We use the kinematics and morphologies of the O iii 5007 Å and H α 6563 Å emission lines redshifted into the near-infrared to gauge the extents, kinetic energies and momentum fluxes of the ionized outflows in the quasars host galaxies. For the ERQs, the galactic-scale outflows are likely driven by radiation pressure in a high column density environment or due to an adiabatic shock. The outflows in the ERQs carry a significant amount of energy ranging from 0.05 to 5 ${{\ \rm per\ cent}}$ of the quasar’s bolometric luminosity, powerful enough to have a significant impact on the quasar host galaxies. The outflows are resolved on kpc scales, the observed outflow sizes are generally smaller than other ionized outflows observed at high redshift. The high ratio between the momentum flux of the ionized outflow and the photon momentum flux from the quasar accretion disc and high nuclear obscuration makes these ERQs great candidates for transitional objects where the outflows are likely responsible for clearing material in the inner regions of each galaxy, unveiling the quasar accretion disc at optical wavelengths.
ABSTRACT Emission from metal resonant lines has recently emerged as a potentially powerful probe of the structure of galactic winds at low and high redshift. In this work, we present only the second ...example of spatially resolved observations of Na i D emission from a galactic wind in a nearby galaxy (and the first 3D observations at any redshift). F05189-2524, a nearby (z = 0.0428) ultraluminous infrared galaxy powered by a quasar, was observed with the integral field unit on the Gemini Multi-Object Spectrograph at Gemini South. Na i D absorption in the system traces dusty filaments on the near side of an extended, active galactic nucleus-driven galactic wind (with projected velocities up to 2000 km s−1). These filaments ( and cm−2) simultaneously obscure the stellar continuum and Na i D emission lines. The Na i D emission lines serve as a complementary probe of the wind: they are strongest in regions of low foreground obscuration and extend up to the limits of the field of view (galactocentric radii of 3 kpc). An azimuthally symmetric Sérsic model extincted by the same foreground screen as the stellar continuum reproduces the Na i D emission line surface brightness distribution except in the inner regions of the wind, where some emission-line filling of absorption lines may occur. The presence of detectable Na i D emission in F05189-2524 may be due to its high continuum surface brightness at the rest wavelength of Na i D. These data uniquely constrain current models of cool gas in galactic winds and serve as a benchmark for future observations and models.
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