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Ninety per cent of baryons are located outside galaxies, either in the circumgalactic or intergalactic medium 1 , 2 . Theory points to galactic winds as the primary source of the enriched and massive circumgalactic medium 3 – 6 . Winds from compact starbursts have been observed to flow to distances somewhat greater than ten kiloparsecs 7 – 10 , but the circumgalactic medium typically extends beyond a hundred kiloparsecs 3 , 4 . 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 11 , 12 . Theory predicts that winds expel baryons from galaxies into intergalactic space; now optical observations of the massive, but compact, galaxy SDSS J211824.06+001729.4 show that it is ejecting an enormous ionized outflow of gas.

We use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (α cum ∼ 0.6) down to L X ∼ 10 36 erg s −1 . We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).

We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate (SFR), dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative two-dimensional bulge/disk decomposition of the 2MASS/\\(K_{s}\\)-band images of the SFRS galaxies yields global luminosity and stellar mass functions, along with separate mass functions for their bulges and disks. These accurate mass functions cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infra-red luminosity, unbiased by AGN content and environment. We measure an integrated luminosity density \\(j\\) = 1.72 \\(\\pm\\) 0.93 \\(\\times\\) 10\\(^{9}\\) L\\(_{\\odot}\\) \\(h^{-1}\\) Mpc\\(^{-3}\\) and a total stellar mass density \\(\\rho_{M}\\) = 4.61 \\(\\pm\\) 2.40 \\(\\times\\) 10\\(^{8}\\) M\\(_{\\odot}\\) \\(h^{-1}\\) Mpc\\(^{-3}\\). While the stellar mass of the \\emph{average} star-forming galaxy is equally distributed between its sub-components, disks globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disk stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and disks of local (\\(z = 0\\)) star-forming galaxies.

We present results on the properties of extreme gas outflows in massive (\\(\\rm M_* \\sim\\)10\\(^{11} \\ \\rm M_{\\odot}\\)), compact, starburst ($\\rm SFR \\sim$$200 \\, \\rm M_{\\odot} \\ yr^{-1}\\() galaxies at z = \\)0.4-0.7\\( with very high star formation surface densities (\\)\\rm \\Sigma_{SFR} \\sim$$2000 \\,\\rm M_{\\odot} \\ yr^{-1} \\ kpc^{-2}\\(). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies we identify outflows with maximum velocities of \\)820 - 2860\\( \\kmps. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T \\)\\sim\\(10\\)^4\\( K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously-distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies' star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong \\mgii \\ absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of \\)\\rm \\sim\\(50 \\)-\\( 2200 \\)\\rm M_{\\odot} \\, yr^{-1}\\(, assuming a fiducial outflow size of 5 kpc, and mass loading factors of \\)\\eta\\sim\\(5 for most of the sample. %with \\)\\eta\\sim$20 for two galaxies. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution.

The Makani galaxy hosts the poster child of a galactic wind on scales of the circumgalactic medium. It consists of a two-episode wind in which the slow, outer wind originated 400 Myr ago (Episode I; R_I = 20-50 kpc) and the fast, inner wind is 7 Myr old (Episode II; R_II = 0-20 kpc). While this wind contains ionized, neutral, and molecular gas, the physical state and mass of the most extended phase--the warm, ionized gas--is unknown. Here we present Keck optical spectra of the Makani outflow. These allow us to detect hydrogen lines out to r = 30-40 kpc and thus constrain the mass, momentum, and energy in the wind. Many collisionally-excited lines are detected throughout the wind, and their line ratios are consistent with 200-400 km/s shocks that power the ionized gas, with v_shock = \\(\\sigma\\)_wind. Combining shock models, density-sensitive line ratios, and mass and velocity measurements, we estimate that the ionized mass and outflow rate in the Episode II wind could be as high as that of the molecular gas: M_II(HII) ~ M_II(H_2) = (1-2)x10^9 Msun and dM/dt_II(HII) ~ dM/dt_II(H_2) = 170-250 Msun/yr. The outer wind has slowed, so that dM/dt_I(HII) ~ 10 Msun/yr, but it contains more ionized gas: M_I(HII) = 5x10^9 Msun. The momentum and energy in the recent Episode II wind imply a momentum-driven flow (p ``boost\" ~ 7) driven by the hot ejecta and radiation pressure from the Eddington-limited, compact starburst. Much of the energy and momentum in the older Episode I wind may reside in a hotter phase, or lie further into the CGM.

We present a measurement of the intrinsic space density of intermediate redshift (\\(z\\sim0.5\\)), massive (\\(M_{*} \\sim 10^{11} \\ \\text{M}_{\\odot}\\)), compact (\\(R_{e} \\sim 100\\) pc) starburst (\\(\\Sigma_{SFR} \\sim 1000 \\ \\text{M}_{\\odot} \\ \\text{yr}^{-1} \\text{kpc}^{-1}\\)) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec scale, \\(>1000 \\ \\text{km}\\ \\text{s}^{-1}\\) outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale for which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for \\(\\sim 148 ^{+27}_{-24}\\) Myr and have an intrinsic space density \\(n_{\\text{CS}} \\sim (1.1^{+0.5}_{-0.3}) \\times 10^{-6} \\ \\ \\text{Mpc}^{-3}\\). This space density is broadly consistent with our \\(z\\sim0.5\\) compact starbursts being the most extremely compact and star forming low redshift analogs of the compact star forming galaxies in the early Universe as well as them being the progenitors to a fraction of intermediate redshift post starburst and compact quiescent galaxies.

We present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive (\\(\\rm M_* \\sim 10^{11} M_{\\odot}\\)), compact starburst galaxies at z = 0.4-0.7. We use data from Keck/NIRSPEC, SDSS, Gemini/GMOS, MMT, and Magellan/MagE to measure rest-frame optical and near-IR spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean \\(\\rm \\Sigma_{SFR} \\sim 3000 \\,M_{\\odot} yr^{-1} kpc^{-2}\\)) and powerful galactic outflows (maximum speeds v\\(_{98} \\sim\\) 1000-3000 km s\\(^{-1}\\)). Our unique data set includes an ensemble of both emission [OII]\\(\\lambda\\lambda\\)3726,3729, H\\(\\beta\\), [OIII]\\(\\lambda\\lambda\\)4959,5007, H\\(\\alpha\\), [NII]\\(\\lambda\\lambda\\)6548,6583, and [SII]\\(\\lambda\\lambda\\)6716,6731) and absorption MgII\\(\\lambda\\lambda\\)2796,2803, and FeII\\(\\lambda\\)2586) lines that allow us to investigate the kinematics of the cool gas phase (T\\(\\sim\\)10\\(^4\\) K) in the outflows. Employing a suite of line ratio diagnostic diagrams, we find that the central starbursts are characterized by high electron densities (median n\\(_e \\sim\\) 530 cm\\(^{-3}\\)), and high metallicity (solar or super-solar). We show that the outflows are most likely driven by stellar feedback emerging from the extreme central starburst, rather than by an AGN. We also present multiple intriguing observational signatures suggesting that these galaxies may have substantial Lyman continuum (LyC) photon leakage, including weak [SII] nebular emission lines. Our results imply that these galaxies may be captured in a short-lived phase of extreme star formation and feedback where much of their gas is violently blown out by powerful outflows that open up channels for LyC photons to escape.

High-velocity outflows are ubiquitous in compact, massive (M\\(_* \\sim\\) 10\\(^{11}\\) M\\(_{\\odot}\\)), z \\(\\sim\\) 0.5 galaxies with extreme star formation surface densities (\\(\\Sigma_{SFR} \\sim\\) 2000 M\\(_{\\odot}\\) yr\\(^{-1}\\) kpc\\(^{-2}\\)). We have previously detected and characterized these outflows using MgII absorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [OII] and MgII emission nebulae surrounding all of the 12 galaxies in this study. We find that [OII] is more effective than MgII in tracing low surface brightness, extended emission in these galaxies. The [OII] nebulae are spatially extended beyond the stars, with radial extent R\\(_{90}\\) between 10 and 40 kpc. The nebulae exhibit non-gravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from -335 to -1920 km s\\(^{-1}\\). The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last \\(<\\) 3 Myr) exhibit the highest central velocity dispersions (\\(\\sigma >\\) 400 km s\\(^{-1}\\)), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the CGM and mix on timescales \\(>\\) 50 Myr.

Feedback through energetic outflows has emerged as a key physical process responsible for transforming star-forming galaxies into the quiescent systems observed in the local universe. To explore this process, this paper focuses on a sample of massive and compact merger remnant galaxies hosting high-velocity gaseous outflows (\\(|v| \\gtrsim 10^{3}\\) km s\\(^{-1}\\)), found at intermediate redshift (\\(z \\sim 0.6\\)). From their mid-infrared emission and compact morphologies, these galaxies are estimated to have exceptionally large star formation rate (SFR) surface densities (\\(\\Sigma_{SFR} \\sim 10^{3}\\) \\(\\mathrm{M_{\\odot}}\\) yr\\(^{-1}\\) kpc\\(^{-2}\\)), approaching the Eddington limit for radiation pressure on dust grains. This suggests that star formation feedback may be driving the observed outflows. However, these SFR estimates suffer from significant uncertainties. We therefore sought an independent tracer of star formation to probe the compact starburst activity in these systems. In this paper, we present SFR estimates calculated using 1.5 GHz continuum Jansky Very Large Array observations for 19 of these galaxies. We also present updated infrared (IR) SFRs calculated from WISE survey data. We estimate SFRs from the IR to be larger than those from the radio for 16 out of 19 galaxies by a median factor of 2.5. We find that this deviation is maximized for the most compact galaxies hosting the youngest stellar populations, suggesting that compact starbursts deviate from the IR-radio correlation. We suggest that this deviation stems either from free-free absorption of synchrotron emission, a difference in the timescale over which each indicator traces star formation, or exceptionally hot IR-emitting dust in these ultra-dense galaxies.

We present multi-band Hubble Space Telescope imaging that spans rest-frame near-ultraviolet through near-infrared wavelengths (0.3-1.1 \\(\\mu\\)m) for 12 compact starburst galaxies at z=0.4-0.8. These massive galaxies (M_stellar ~ 10^11 M_Sun) are driving very fast outflows (\\(v_{max}\\)=1000-3000 km/s), and their light profiles are dominated by an extremely compact starburst component (half-light radius ~ 100 pc). Our goal is to constrain the physical mechanisms responsible for launching these fast outflows by measuring the physical conditions within the central kiloparsec. Based on our stellar population analysis, the central component typically contributes \\(\\approx\\)25% of the total stellar mass and the central escape velocities \\(v_{esc,central}\\approx900\\) km/s are a factor of two smaller than the observed outflow velocities. This requires physical mechanisms that can accelerate gas to speeds significantly beyond the central escape velocities, and it makes clear that these fast outflows are capable of traveling into the circumgalactic medium, and potentially beyond. We find central stellar densities comparable to theoretical estimates of the Eddington limit, and we estimate \\(\\Sigma_1\\) surface densities within the central kpc comparable to those of compact massive galaxies at \\(0.5

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