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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.

A new class of extragalactic astronomical sources discovered in 2021, named odd radio circles (ORCs) 1 , are large rings of faint, diffuse radio continuum emission spanning approximately 1 arcminute on the sky. Galaxies at the centres of several ORCs have photometric redshifts of z  ≃ 0.3–0.6, implying physical scales of several 100 kpc in diameter for the radio emission, the origin of which is unknown. Here we report spectroscopic data on an ORC including strong [O ii ] emission tracing ionized gas in the central galaxy of ORC4 at z  = 0.4512. The physical extent of the [O ii ] emission is approximately 40 kpc in diameter, larger than expected for a typical early-type galaxy 2 but an order of magnitude smaller than the large-scale radio continuum emission. We detect an approximately 200 km s −1 velocity gradient across the [O ii ] nebula, as well as a high velocity dispersion of approximately 180 km s −1 . The [O ii ] equivalent width (approximately 50 Å) is extremely high for a quiescent galaxy. The morphology, kinematics and strength of the [O ii ] emission are consistent with the infall of shock ionized gas near the galaxy, following a larger, outward-moving shock. Both the extended optical and radio emission, although observed on very different scales, may therefore result from the same dramatic event. We find that the optical emission due to ionized gas that is characteristic of a shock extends 40 kpc in diameter across the host galaxy of an odd radio circle.

Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars. Counter-rotating gases demonstrate external gas acquisition in galaxies, but their presence in blue, star-forming galaxies has not been studied systematically. Here, the authors analyse the MaNGA survey data to find a fraction of counter-rotators among blue galaxies whose central regions show ongoing growth.

Many astronomers now participate in large international scientific collaborations, and it is important to examine whether these structures foster a healthy scientific climate that is inclusive and diverse. The Committee on the Participation of Women in the Sloan Digital Sky Survey (CPWS) was formed to evaluate the demographics and gender climate within SDSS-IV, one of the largest and most geographically distributed astronomical collaborations. In 2014 April, the CPWS administered a voluntary demographic survey to establish a baseline for the incipient SDSS-IV, which began observations in 2014 July. We received responses from 250 participants (46% of the active membership). Half of the survey respondents were located in the United States or Canada and 30% were based in Europe. Approximately 65% were faculty or research scientists and 31% were postdocs or graduate students. Eleven percent of survey respondents considered themselves to be an ethnic minority at their current institution. Twenty-five percent of the SDSS-IV collaboration members are women, a fraction that is consistent with the U.S. astronomical community, but substantially higher than the fraction of women in the International Astronomical Union (16%). Approximately equal fractions of men and women report holding positions of leadership in the collaboration. When binned by academic age and career level, men and women also assume leadership roles at approximately equal rates, in a way that increases steadily for both genders with increasing seniority. In this sense, SDSS-IV has been successful in recruiting leaders that are representative of the collaboration. That said, it is clear that more progress needs to be made toward achieving gender balance and increasing diversity in the field of astronomy, and there is still room for improvement in the membership and leadership of SDSS-IV. For example, at the highest level of SDSS-IV leadership, women disproportionately assume roles related to education and public outreach. The goal of the CPWS is to use these initial data to establish a baseline for tracking demographics over time as we work to assess and improve the climate of SDSS-IV.

Even though galactic winds are common in galaxies with starbursts or active galactic nuclei (AGN), the role of such gas flows in galaxy evolution remains uncertain. Here we examine how winds vary along a likely evolutionary sequence connecting starburst to post-starburst to quiescent galaxies. To detect the interstellar medium and measure its bulk flows, we examine the residual Na D absorption line doublet after the stellar contribution has been removed from each galaxy’s spectrum. We discover that outflows diminish along this sequence, i.e., as star formation ends. We then focus on the wind behavior within the post-starburst sample, for which we have measured the time elapsed since the starburst ended (post-burst age) via detailed modeling of their star formation histories (French et al.2018). Even within our post-starburst sample, the fraction of galaxies with significant winds and the average wind velocities decrease with post-burst age after controlling for stellar mass.

We have obtained ultraviolet spectra between 1150 and 1450 Å of four ultraviolet-bright, infrared-luminous starburst galaxies. Our selected sight-lines towards the starburst nuclei probe the conditions in the starburst-driven outflows. We detect outflowing gas with velocities of up to ∼900 km s−1. It is likely that the outflows are a major source of metal enrichment of the galaxies' halos. The mass outflow rates of several tens of M⊙ yr−1 are similar to the star-formation rates. The outflows may quench star formation and ultimately regulate the starburst.

Ninety per cent of baryons are located outside galaxies, either in the circumgalactic or intergalactic medium.sup.1,2. Theory points to galactic winds as the primary source of the enriched and massive circumgalactic medium.sup.3-6. Winds from compact starbursts have been observed to flow to distances somewhat greater than ten kiloparsecs.sup.7-10, but the circumgalactic medium typically extends beyond a hundred kiloparsecs.sup.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.sup.11,12.

Ninety per cent of baryons are located outside galaxies, either in the circumgalactic or intergalactic medium.sup.1,2. Theory points to galactic winds as the primary source of the enriched and massive circumgalactic medium.sup.3-6. Winds from compact starbursts have been observed to flow to distances somewhat greater than ten kiloparsecs.sup.7-10, but the circumgalactic medium typically extends beyond a hundred kiloparsecs.sup.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.sup.11,12.

Ninety per cent of baryons are located outside galaxies, either in the circumgalactic or intergalactic medium.sup.1,2. Theory points to galactic winds as the primary source of the enriched and massive circumgalactic medium.sup.3-6. Winds from compact starbursts have been observed to flow to distances somewhat greater than ten kiloparsecs.sup.7-10, but the circumgalactic medium typically extends beyond a hundred kiloparsecs.sup.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.sup.11,12.

The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/Hβ versus [NII]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by AGN activity (BPT-AGN). Yet the BPT diagram is limited to z<0.5, the redshift at which [NII]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g−z color, [NeIII]λ3869, and [OII]λλ3726+3729 and can be used for galaxies out to z<1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray selected AGNs as BPT-SF.