Star formation driven galactic winds in UGC 10043 (original) (raw)
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Monthly Notices of the Royal Astronomical Society, 2016
We investigate a sample of 40 local, main-sequence, edge-on disc galaxies using integral field spectroscopy with the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey to understand the link between properties of the extraplanar gas and their host galaxies. The kinematics properties of the extraplanar gas, including velocity asymmetries and increased dispersion, are used to differentiate galaxies hosting large-scale galactic winds from those dominated by the extended diffuse ionized gas. We find rather that a spectrum of diffuse gas-dominated to wind-dominated galaxies exist. The wind-dominated galaxies span a wide range of star formation rates (SFRs; −1 log (SFR/M yr −1) 0.5) across the whole stellar mass range of the sample (8.5 log (M * /M) 11). The wind galaxies also span a wide range in SFR surface densities (10 −3-10 −1.5 M yr −1 kpc −2) that is much lower than the canonical threshold of 0.1 M yr −1 kpc −2. The wind galaxies on average have higher SFR surface densities and higher Hδ A values than those without strong wind signatures. The enhanced Hδ A indicates that bursts of star formation in the recent past are necessary for driving large-scale galactic winds. We demonstrate with Sloan Digital Sky Survey data that galaxies with high SFR surface density have experienced bursts of star formation in the recent past. Our results imply that the galactic winds revealed in our study are indeed driven by bursts of star formation, and thus probing star formation in the time domain is crucial for finding and understanding galactic winds.
Galactic Winds in Cosmological Simulations of the Circumgalactic Medium
2012
We explore new observationally-constrained sub-resolution models of galactic outflows and investigate their impact on the circumgalactic medium (CGM) in the redshift range z = 2 − 4. We perform cosmological hydrodynamic simulations, including star formation, chemical enrichment, and four cases of SNe-driven outflows: no wind (NW), an energy-driven constant velocity wind (CW), a radially varying wind (RVWa) where the outflow velocity has a positive correlation with galactocentric distance (r), and a RVW with additional dependence on halo mass (RVWb). Overall, we find that the outflows expel metal-enriched gas away from galaxies, significantly quench the star formation, reduce the central galactic metallicity and enrich the CGM. At z = 2, the radial profiles of gas properties around galaxy centers are most sensitive to the choice of the wind model for halo masses in the range (10 9 − 10 11)M ⊙. We infer that outflows in the RVWb model are least effective, with results similar to the NW case, except that the CGM is enriched more. Moreover, we find that the models CW and RVWa are similar, both showing the impact of effective winds, with the following notable differences. RVWa causes a greater suppression of star formation rate at z 5, and has a higher fraction of low-density (δ < 10), warm-hot (10 4 − 10 6 K) gas than in CW. Outflows in CW produce a higher and earlier enrichment of some IGM phases than in RVWa. By visual inspection, we note that the RVWa model shows galactic disks more pronounced than all the other wind models. We predict that some observational diagnostics are more promising to distinguish between different outflow driving mechanisms in galaxies: Z C of the CGM gas at r ∼ (30 − 300)h −1 kpc comoving, and CIV fraction of the inner gas at r < (4 − 5)h −1 kpc comoving.
Physical properties of galactic winds using background quasars
Monthly Notices of the Royal Astronomical Society, 2012
We investigate the spatial location of quasar lines-of-sight with strong Mg II absorption (with W λ2796 r > 0.3Å) passing near spectroscopically identified galaxies at z ∼ 0.1. Using a dozen quasar-galaxy pairs available from the literature, we find that the azimuthal orientation of the quasar sight-lines is bi-modal, with about half the Mg II sight-lines aligned with the major axis and the other half within α = 30 • of the minor axis. This dichotomy is also present in the instantaneous star-formation rates (SFRs) of the host. These results indicate that both gaseous disks and strong bipolar outflows contribute to Mg II cross-section. In addition, a simple bi-conical wind model is able to reproduce the observed Mg II kinematics for the sight-lines aligned with the minor axis, showing that bipolar outflows contribute significantly to the Mg II cross-section. Finally, using our kinematic wind model, we can extract directly key wind properties such as the de-projected outflow speed V out of the material traced by Mg II and the outflow rates. The outflow speed V out are found to be 150-300 km s −1 , i.e. of the order of the circular velocity, and smaller than the escape velocity by a factor of ∼ 2. The outflow rates are typically 2 to 3 times the SFRs. Our results provide a test bed for measuring wind properties with greater precision.
On the onset of galactic winds in quiescent star forming galaxies
Context. The hierarchical model of galaxy formation, despite its many successes, still overpredicts the baryons fraction locked in galaxies as a condensed phase. The efficiency of supernovae feedback, proposed a long time ago as a possible solution for this so-called "overcooling" problem, is still under debate, mainly because modelling supernovae explosions within a turbulent interstellar medium, while capturing realistic large scale flows around the galaxy is a very demanding task. Aims. Our goal is to study the effect of supernovae feedback on a disk galaxy, taking into account the impact of infalling gas on both the star formation history and the corresponding outflow structure, the apparition of a supernovae-driven wind being highly sensitive to the halo mass, the galaxy spin and the star formation efficiency. Methods. We model our galaxies as cooling and collapsing NFW spheres. The dark matter component is modelled as a static external potential, while the baryon component is described by the Euler equations using the AMR code RAMSES. Metal-dependent cooling and supernovaeheating are also implemented using state-of-the-art recipes coming from cosmological simulations. We allow for 3 parameters to vary: the halo circular velocity, the spin parameter and the star formation efficiency. Results. We found that the ram pressure of infalling material is the key factor limiting the apparition of galactic winds. We obtain a very low feedback efficiency, with supernovae to wind energy conversion factor around one percent, so that only low circular velocity galaxies give rise to strong winds. For massive galaxies, we obtain a galatic fountain, for which we discuss the observational properties. Conclusions. We conclude that for quiescent isolated galaxies, galactic winds appear only in very low mass systems. Although that can quite efficiently enrich the IGM with metals, they don't carry away enough cold material to solve the overcooling problem.
Discovery of a galactic wind in the central region of M100
Monthly Notices of the Royal Astronomical Society: Letters, 2007
We report the discovery of a galactic wind in the central region of the galaxy M100. This result is based on a careful 2D spectroscopic study performed on observations made with the fibre system INTEGRAL on the WHT. The primary evidence of the wind is the presence of blueshifted interstellar NaD absorption lines. The velocity field of the absorbers show a clear rotation pattern but globally blueshifted (∼ -115 km/s) with respect to the systemic velocity of the galaxy. The emission lines also present a blueward component arising from the ionized gas phase of the galactic wind. The velocity field of the ionized gas wind component shows no evidences of rotation but exhibits a pattern that can be interpreted in terms of the projection of an outflowing cone or shell. The wind component has [NII]/Hα ratios of about 1.8, typical of shock ionization. The ionized component of the wind can be identified with an expanding shell of shocked gas, and the neutral component with disk gas entrained in the wind at the interface of the expanding shell with the galactic ISM. The galactic wind seems to be driven uniquely by the nuclear starburst. Our analysis indicates that a non negligible fraction of the wind material might escape to the IGM. In this case, if the wind detected in M100 were representative of similar phenomena in other galaxies with low to moderate activity, the current estimates of metal and dust content of the IGM might be drastically underestimated.
Annual Review of Astronomy and Astrophysics, 2005
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.
Galactic Winds 1 Galactic Winds
2005
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.