An official website of the United States government
Abstract Shocked POstarburst Galaxies (SPOGs) exhibit both emission lines suggestive of shock-heated gas and poststarburst-like stellar absorption, resulting in a unique subset for galaxy evolution studies. We have observed 77 galaxies that fulfilled the SPOG criteria selection using the DeVeny Spectrograph on the Lowell Discovery Telescope. Our long-slit minor axis spectra detect Hαand [OIII] in some SPOGs out to 6 kpc above the galactic plane. We find extraplanar ionized gas in 31 targets of our sample overall. Using their internal and external kinematics, we argue that 22 galaxies host outflows with ionized gas masses ranging from 102M⊙to 105M⊙. The rest are likely extended diffuse ionized gas. A positive correlation exists between active galactic nuclei (AGN) luminosity and the extraplanar gas extent, velocity dispersion, and mass—suggesting that the AGN may indeed drive the outflows detected in AGN hosts. The low masses of the extraplanar gas suggest that these outflows are not depleting each galaxy’s gas reserves. The outflows, therefore, are not likely a significant quenching mechanism in these SPOGs.
more »
« less
Ionized Gas Outflows in the Galaxy and Mass Assembly (GAMA) Survey: Signatures of AGN Feedback in Low-mass Galaxies
Abstract We present a sample of 398 galaxies with ionized gas outflow signatures in their spectra from the Galaxy and Mass Assembly Survey Data Release 4, including 45 low-mass galaxies with stellar massesM* < 1010M⊙. We assemble our sample by systematically searching for the presence of a second velocity component in the [O iii]λλ4959, 5007 doublet emission line in 39,612 galaxies with redshiftsz < 0.3. The host galaxies are classified using the Baldwin–Phillips–Terlevich diagram, with ~89% identified as active galactic nuclei (AGNs) and composites and 11% as star-forming (SF) galaxies. The outflows are typically faster in AGNs with a median velocity of 936 km s−1compared to 655 km s−1in the SF objects. Of particular interest are the 45 galaxies in the low-mass range, of which a third are classified as AGNs/composites. The outflows from the low-mass AGNs are also faster and more blueshifted compared to those in the low-mass SF galaxies. This indicates that black hole outflows can affect host galaxies in the low-mass range and that AGN feedback in galaxies withM* < 1010M⊙should be considered in galaxy evolution models.
more »
« less
- Award ID(s):
- 2235277
- PAR ID:
- 10597709
- Publisher / Repository:
- The Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 979
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 26
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We present results on the properties of extreme gas outflows in massive (M*∼ 1011M⊙), compact, starburst (star formation rate, SFR∼ 200M⊙yr−1) galaxies atz= 0.4–0.7 with very high star formation surface densities (ΣSFR∼ 2000M⊙yr−1kpc−2). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s−1. 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∼ 104K). 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 Mgiiabsorption 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 ∼50–2200M⊙yr−1, assuming a fiducial outflow size of 5 kpc, and mass loading factors ofη∼ 5 for most of the sample. 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.more » « less
-
Abstract High-velocity outflows are ubiquitous in compact, massive (M*∼ 1011M⊙),z∼ 0.5 galaxies with extreme star formation surface densities (ΣSFR∼ 2000M⊙yr−1kpc−2). We have previously detected and characterized these outflows using Mgiiabsorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [Oii] and Mgiiemission nebulae surrounding all of the 12 galaxies in this study. We find that [Oii] is more effective than Mgiiin tracing low surface brightness, extended emission in these galaxies. The [Oii] nebulae are spatially extended beyond the stars, with radial extentR90between 10 and 40 kpc. The nebulae exhibit nongravitational 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 (σ≳ 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 circumgalactic medium and mix on timescales ≳50 Myr.more » « less
-
Abstract We present an analysis of Hubble Space Telescope COS/G160M observations of CIVin the inner circumgalactic medium (CGM) of a novel sample of eightz∼ 0,L≈L⋆galaxies, paired with UV-bright QSOs at impact parameters (Rproj) between 25 and 130 kpc. The galaxies in this stellar-mass-controlled sample (log10M⋆/M⊙∼ 10.2–10.9M⊙) host supermassive black holes (SMBHs) with dynamically measured masses spanning log10MBH/M⊙∼ 6.8–8.4; this allows us to compare our results with models of galaxy formation where the integrated feedback history from the SMBH alters the CGM over long timescales. We find that the CIVcolumn density measurements (NC IV; average log10NC IV,CH= 13.94 ± 0.09 cm−2) are largely consistent with existing measurements from other surveys ofNC IVin the CGM (average log10NC IV,Lit= 13.90 ± 0.08 cm−2), but do not show obvious variation as a function of the SMBH mass. By contrast, specific star formation rate (sSFR) is highly correlated with the ionized content of the CGM. We find a large spread in sSFR for galaxies with log10MBH/M⊙> 7.0, where the CGM CIVcontent shows a clear dependence on galaxy sSFR but notMBH. Our results do not indicate an obvious causal link between CGM CIVand the mass of the galaxy’s SMBH; however, through comparisons to the EAGLE, Romulus25, and IllustrisTNG simulations, we find that our sample is likely too small to constrain such causality.more » « less
-
Abstract The baryon cycle is crucial for understanding galaxy formation, as gas inflows and outflows vary throughout a galaxy’s lifetime and affect its star formation rate. Despite the necessity of accretion for galaxy growth at high redshifts, direct observations of inflowing gas have proven elusive, especially atz ≳ 2. We present a spectroscopic analysis of a galaxy at redshiftz= 2.45, which exhibits signs of inflow in several ultraviolet interstellar absorption lines, with no clear outflow signatures. The absorption lines are redshifted by ∼250 km s−1with respect to the systemic redshift, and Civshows a prominent inverse P-Cygni profile. Simple stellar population models suggest that this galaxy has a low metallicity (∼5% solar), with a very young starburst of age ∼4 Myr dominating the ultraviolet luminosity. The gas inflow velocity and nebular velocity dispersion suggest an approximate halo mass of order ∼1011M⊙, a regime in which simulations predict that bursty star formation is common at this redshift. We conclude that this system is likely in the beginning of a cycle of bursty star formation, where inflow and star formation rates are high, but where supernovae and other feedback processes have not yet launched strong outflows. In this scenario, we expect the inflow-dominated phase to be observable (e.g., with net redshifted interstellar medium absorption) for only a short timescale after a starburst onset. This result represents a promising avenue for probing the full baryon cycle, including inflows, during the formative phases of low-mass galaxies at high redshifts.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/1538-4357/ad9a57
