The SAMI Galaxy Survey: shocks and outflows in a normal star-forming galaxy (original) (raw)
Related papers
The Astronomical …, 2010
We analyze star forming galaxies drawn from SDSS DR7 to show how the interstellar medium (ISM) Na I λλ5890, 5896 (Na D) absorption lines depend on galaxy physical properties, and to look for evidence of galactic winds. We combine the spectra of galaxies with similar geometry/physical parameters to create composite spectra with signal-to-noise ∼ 300. The stellar continuum is modeled using stellar population synthesis models, and the continuum-normalized spectrum is fit with two Na I absorption components. We find that: (1) ISM Na D absorption lines with equivalent widths EW > 0.8 Å are only prevalent in disk galaxies with specific properties -large extinction (A V ), high star formation rates (SFR), high star formation rate per unit area (Σ SFR ), or high stellar mass (M * ).
2016
We present an analysis of the Mg II λλ2796, 2803 and Fe II λλ2586, 2600 absorption line profiles in individual spectra of 105 galaxies at 0.3 < z < 1.4. The galaxies, drawn from redshift surveys of the GOODS fields and the Extended Groth Strip, fully sample the range in star formation rates (SFRs) occupied by the star-forming sequence with stellar masses log M * /M ⊙ 9.5 at 0.3 < z < 0.7. Using the Doppler shifts of the Mg II and Fe II absorption lines as tracers of cool gas kinematics, we detect large-scale winds in 66 ± 5% of the galaxies. High-resolution Hubble Space Telescope/Advanced Camera for Surveys imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ∼ 89% of galaxies having inclinations (i) < 30 • (face-on), while the wind detection rate is only ∼ 45% in objects having i > 50 • (edge-on). Combined with the comparatively weak dependence of the wind detection rate on intrinsic galaxy properties (including SFR surface density), this suggests that biconical outflows are ubiquitous in normal, starforming galaxies at z ∼ 0.5, with over half of the sample having full wind cone opening angles of ∼ 100 •. We find that the wind velocity is correlated with host galaxy M * at 3.4σ significance, while the equivalent width (EW) of the flow is correlated with host galaxy SFR at 3.5σ significance, suggesting that hosts with higher SFR may launch more material into outflows and/or generate a larger velocity spread for the absorbing clouds. The large (> 1Å) Mg II outflow EWs typical of this sample are rare in the context of Mg II absorption studies along QSO sightlines probing the extended halos of foreground galaxies, implying that this wind material is not often detected at impact parameters > 10 kpc. Assuming that the gas is launched into dark matter halos with simple, isothermal density profiles, the wind velocities measured for the bulk of the cool material (∼ 200 − 400 km s −1) are sufficient to enable escape from the halo potentials only for the lowest-M * systems in the sample. However, the highest-velocity gas in the outflows typically carries sufficient energy to reach distances of 50 kpc, and may therefore be a viable source of cool material for the massive circumgalactic medium observed around bright galaxies at z ∼ 0.
arXiv (Cornell University), 2019
We investigate the prevalence of galactic-scale outflows in post-starburst (PSB) galaxies at high redshift (1 < z < 1.4), using the deep optical spectra available in the UKIDSS Ultra Deep Survey (UDS). We use a sample of ∼40 spectroscopically confirmed PSBs, recently identified in the UDS field, and perform a stacking analysis in order to analyse the structure of strong interstellar absorption features such as Mg II (λ2800 Å). We find that for massive (M * > 10 10 M) PSBs at z > 1, there is clear evidence for a strong blue-shifted component to the Mg II absorption feature, indicative of high-velocity outflows (v out ∼ 1150 ± 160 km s −1) in the interstellar medium. We conclude that such outflows are typical in massive PSBs at this epoch, and potentially represent the residual signature of a feedback process that quenched these galaxies. Using full spectral fitting, we also obtain a typical stellar velocity dispersion σ * for these PSBs of ∼ 200 km s −1 , which confirms they are intrinsically massive in nature (dynamical mass M d ∼ 10 11 M). Given that these high-z PSBs are also exceptionally compact (r e ∼ 1-2 kpc) and spheroidal (Sérsic index n ∼ 3), we propose that the outflowing winds may have been launched during a recent compaction event (e.g. major merger or disc collapse) that triggered either a centralized starburst or active galactic nuclei (AGN) activity. Finally, we find no evidence for AGN signatures in the optical spectra of these PSBs, suggesting they were either quenched by stellar feedback from the starburst itself, or that if AGN feedback is responsible, the AGN episode that triggered quenching does not linger into the post-starburst phase.
The SAMI Galaxy Survey: gas streaming and dynamical M/L in rotationally supported systems
Monthly Notices of the Royal Astronomical Society, 2015
Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric fits out to r ∼ 2r e. For 12/14 with measured H I profiles, ionized gas and H I maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial light profile as nested, very flattened mass homeoids viewed as a Sérsic form. Fitting broad-band spectral energy distributions to Sloan Digital Sky Survey images gave median stellar mass/light 1.7 assuming a Kroupa initial mass function (IMF) versus 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM distributed like starlight across the SAMI aperture that came to dominate motions as the starlight CSCs declined rapidly. The rest had mass distributed differently from light. Subtracting fits of Sérsic radial profiles to 13 VIKING Z-band images revealed residual weak bars. Near the bar major axis, we assessed m = 2 streaming velocities, and found deviations usually <30 km s −1 from the CSC; three showed no deviation. Thus, asymmetries rarely influenced the CSC despite colocated shock-indicating, emission-line flux ratios in more than 2/3 of our sample.
Monthly Notices of the Royal Astronomical Society
We investigate the energy sources of random turbulent motions of ionised gas from Hα emission in eight local star-forming galaxies from the Sydney-AAO Multiobject Integral field spectrograph (SAMI) Galaxy Survey. These galaxies satisfy strict pure star-forming selection criteria to avoid contamination from active galactic nuclei (AGN) or strong shocks/outflows. Using the relatively high spatial and spectral resolution of SAMI, we find that-on sub-kpc scales our galaxies display a flat distribution of ionised gas velocity dispersion as a function of star formation rate (SFR) surface density. A major fraction of our SAMI galaxies shows higher velocity dispersion than predictions by feedback-driven models, especially at the low SFR surface density end. Our results suggest that additional sources beyond star formation feedback contribute to driving random motions of the interstellar medium (ISM) in star-forming galaxies. We speculate that gravity, galactic shear, and/or magnetorotational instability (MRI) may be additional driving sources of turbulence in these galaxies.
Shock Excitation in Interacting Galaxies: Markarian 266
The Astrophysical Journal, 2000
We present near infrared data on the luminous interacting system Mkn 266 (NGC 5256), comprising 2 µm continuum, and Brγ and 1-0 S(1) emission line images, together with K-band spectra. We have fitted stellar templates to the continuum, allowing us to account for all the stellar features and hence detect even faint gas excitation emission lines, including 8 and 11 H 2 lines in the SW and NE nuclei respectively. Population diagrams for the excited H 2 molecules indicate that most of the 1-0 S(1) in each of the nuclei has a thermal origin. We discuss this with reference to the observed morphologies, especially that of the 1-0 S(1) line. In particular, the core of 1-0 S(1) in the NE nucleus is more compact than the 2 µm continuum; while in the SW nucleus the 1-0 S(1) is significantly offset by 500 pc from the continuum (and other) emission. Lastly we address the issue of the region midway between the two nuclei, where previously a strong source of radio continuum has been observed. These results are set in the context of interacting galaxies where shock excited emission might be expected to occur as a direct consequence of the interaction.
The Astrophysical Journal Supplement Series, 2009
We have analyzed FUSE (905-1187Å) spectra of a sample of 16 local starburst galaxies. These galaxies cover almost three orders of magnitude in starformation rates and over two orders of magnitude in stellar mass. Absorption features from the stars and interstellar medium are observed in all the spectra. The strongest interstellar absorption features are generally blue-shifted by ∼ 50 to 300 km s −1 , implying the almost ubiquitous presence of starburst-driven galactic winds in this sample. The outflow velocites increase with both the star formation rate and the star formation rate per unit stellar mass, consistent with a galactic wind driven by the population of massive stars. We find outflowing coronal-phase gas (T ∼ 10 5.5 K) detected via the O VI absorption-line in nearly every galaxy. The O VI absorption-line profile is optically-thin, is generally weak near the galaxy systemic velocity, and has a higher mean outflow velocity than seen in the lower ionization lines. The relationship between the line width and column density for the O VI absorbing gas is in good agreement with expectations for radiatively cooling and outflowing gas. Such gas will be created in the interaction of the hot out-rushing wind seen in X-ray emission and cool dense ambient material. O VI emission is not generally detected in our sample, suggesting that radiative cooling by the coronal gas is not dynamically significant in draining energy from galactic winds. We find that the measured outflow velocities in the HI and HII phases of the interstellar gas in a given galaxy increase with the strength (equivalent width) of the absorption feature and not with the a FUV luminosity derived from FUSE LiF 2A continuum flux at 1150Å. Values are corrected for MW extinction using the method of and the E(B-V) values given in this table.
The Astrophysical Journal, 2014
We present an analysis of the Mg II λλ2796, 2803 and Fe II λλ2586, 2600 absorption line profiles in individual spectra of 105 galaxies at 0.3 < z < 1.4. The galaxies, drawn from redshift surveys of the GOODS fields and the Extended Groth Strip, fully sample the range in star formation rates (SFRs) occupied by the star-forming sequence with stellar masses log M * /M ⊙ 9.5 at 0.3 < z < 0.7. Using the Doppler shifts of the Mg II and Fe II absorption lines as tracers of cool gas kinematics, we detect large-scale winds in 66 ± 5% of the galaxies. High-resolution Hubble Space Telescope/Advanced Camera for Surveys imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ∼ 89% of galaxies having inclinations (i) < 30 • (face-on), while the wind detection rate is only ∼ 45% in objects having i > 50 • (edge-on). Combined with the comparatively weak dependence of the wind detection rate on intrinsic galaxy properties (including SFR surface density), this suggests that biconical outflows are ubiquitous in normal, starforming galaxies at z ∼ 0.5, with over half of the sample having full wind cone opening angles of ∼ 100 • . We find that the wind velocity is correlated with host galaxy M * at 3.4σ significance, while the equivalent width (EW) of the flow is correlated with host galaxy SFR at 3.5σ significance, suggesting that hosts with higher SFR may launch more material into outflows and/or generate a larger velocity spread for the absorbing clouds. The large (> 1Å) Mg II outflow EWs typical of this sample are rare in the context of Mg II absorption studies along QSO sightlines probing the extended halos of foreground galaxies, implying that this wind material is not often detected at impact parameters > 10 kpc. Assuming that the gas is launched into dark matter halos with simple, isothermal density profiles, the wind velocities measured for the bulk of the cool material (∼ 200 − 400 km s −1 ) are sufficient to enable escape from the halo potentials only for the lowest-M * systems in the sample. However, the highest-velocity gas in the outflows typically carries sufficient energy to reach distances of 50 kpc, and may therefore be a viable source of cool material for the massive circumgalactic medium observed around bright galaxies at z ∼ 0.
Low-Ionization Line Emission from a Starburst Galaxy: A New Probe of a Galactic-Scale Outflow
The Astrophysical Journal, 2011
We study the kinematically narrow, low-ionization line emission from a bright, starburst galaxy at z = 0.69 using slit spectroscopy obtained with Keck/LRIS. The spectrum reveals strong absorption in Mg II and Fe II resonance transitions with Doppler shifts of −200 to −300 km s −1 , indicating a cool gas outflow. Emission in Mg II near and redward of systemic velocity, in concert with the observed absorption, yields a P Cygni-like line profile similar to those observed in the Lyα transition in Lyman Break Galaxies. Further, the Mg II emission is spatially resolved, and extends significantly beyond the emission from stars and H II regions within the galaxy. Assuming the emission has a simple, symmetric surface brightness profile, we find that the gas extends to distances 7 kpc. We also detect several narrow Fe II* fine-structure lines in emission near the systemic velocity, arising from energy levels which are radiatively excited directly from the ground state. We suggest that the Mg II and Fe II* emission is generated by photon scattering in the observed outflow, and emphasize that this emission is a generic prediction of outflows. These observations provide the first direct constraints on the minimum spatial extent and morphology of the wind from a distant galaxy. Estimates of these parameters are crucial for understanding the impact of outflows in driving galaxy evolution.
arXiv: Astrophysics of Galaxies, 2021
We characterize the ionized gas outflows in 15 low-redshift star-forming galaxies, a Valparaíso ALMA Line Emission Survey (VALES) subsample, using MUSE integral field spectroscopy and GAMA photometric broadband data. We measure the emissionline spectra by fitting a double-component profile, with the second and broader component being related to the outflowing gas. This interpretation is in agreement with the correlation between the observed star-formation rate surface density (Σ SFR) and the secondcomponent velocity dispersion (σ 2nd), expected when tracing the feedback component. By modelling the broadband spectra with spectra energy distribution (SED) fitting and obtaining the star-formation histories of the sample, we observe a small decrease in SFR between 100 and 10 Myr in galaxies when the outflow Hα luminosity contribution is increased, indicating that the feedback somewhat inhibits the star formation within these timescales. The observed emission-line ratios are best reproduced by photoionization models when compared to shock-ionization, indicating that radiation from young stellar population is dominant, and seems to be a consequence of a continuous star-formation activity instead of a bursty event. The outflow properties such as mass outflow rate (∼ 0.1 M yr −1), outflow kinetic power (∼ 5.2 × 10 −4 %L bol) and mass loading factor (∼ 0.12) point towards a scenario where the measured feedback is not strong and has a low impact on the evolution of galaxies in general.