Starburst-driven Superwinds in Quasar Host Galaxies (original) (raw)
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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.
Absorption‐Line Probes of Gas and Dust in Galactic Superwinds
The Astrophysical Journal Supplement Series, 2000
We have obtained moderate resolution (R = a few thousand) spectra of the NaIλλ5890,5896 (NaD) absorption-line in a sample of 32 far-IR-bright starburst galaxies. In 18 cases, the NaD line in the nucleus is produced primarily by interstellar gas, while cool stars contribute significantly in the others. In 12 of the 18 "interstellar-dominated" cases the NaD line is blueshifted by over 100 km s −1 relative to the galaxy systemic velocity (the "outflow sources"), while no case shows a net redshift of more than 100 km s −1 . The absorption-line profiles in these outflow sources span the range from near the galaxy systemic velocity to a maximum blueshift of ∼ 400 to 600 km s −1 . The outflow sources are galaxies systematically viewed more nearly face-on than the others. We therefore argue that the absorbing material consists of ambient interstellar material that has been entrained and accelerated along the minor axis of the galaxy by a hot starburst-driven superwind. The NaD lines are optically-thick, but indirect arguments imply total Hydrogen column densities of N H ∼ few ×10 21 cm −2 . This implies that the superwind is expelling matter at a rate comparable to the star-formation rate. This outflowing material is evidently very dusty: we find a strong correlation between the depth of the NaD profile and the line-of-sight reddening. Typical implied values are E(B − V ) = 0.3 to 1 over regions several-to-ten kpc in size. We briefly consider some of the potential implications of these observations. The estimated terminal velocities of superwinds inferred from the present data and extant X-ray data are typically 400 to 800 km s −1 , are independent of the galaxy rotation speed, and are comparable to (substantially exceed) the escape velocities for L * (dwarf) galaxies. The resulting selective loss of metals from shallower potential wells can establish the mass-metallicity relation in spheroids, produce the observed metallicity in the intra-cluster medium, and enrich a general IGM to of-order 10 −1 solar metallicity. If the outflowing dust grains can survive their journey into the IGM, their effect on observations of cosmologically-distant objects would be significant.
The Astronomical Journal, 2000
Arcsecond-resolution X-ray imaging of the nucleus of the nearby starburst galaxy NGC 253 with Chandra reveals a well-collimated, strongly limb-brightened, kiloparsec-scale conical outflow from the central starburst region. The outflow is very similar in morphology to the known Hα outflow cone, on scales down to 20 pc. This provides, for the first time, robust evidence that both X-ray and Hα emission come from low volume filling factor regions of interaction between the fast energetic wind of SN-ejecta and the denser ambient interstellar medium (ISM), and not from the wind fluid itself. We provide estimates of the (observationally and theoretically important) filling factor of the X-ray emitting gas, of between ∼ 4 and 40 per cent, consistent with an upper limit of ∼ 40 per cent based directly on the observed limb-brightened morphology of the outflow. Only 20 per cent of the observed X-ray emission can come from the volume-filling, metal-enriched, wind fluid itself. Spatially-resolved spectroscopy of the soft diffuse thermal X-ray emission reveals that the predominant source of spectral variation along the outflow cones is due to strong variation in the absorption, on scales of ∼ 60 pc, there being little change in the characteristic temperature of the emission. We show that these observations are easily explained by, and fully consistent with, the standard model of a superwind driven by a starburst of NGC 253's observed power. If these results are typical of all starburst-driven winds, then we do not directly see all the energy and gas (in particular the hot metal-enriched gas) transported out of galaxies by superwinds, even in X-ray emission.
The WISSH Quasars Project IV . BLR versus kpc-scale winds
2018
AGN-driven winds are invoked in the most successful models of galaxy evolution to explain the observed physical and evolutionary properties of massive galaxies. Winds are expected to deposit energy and momentum into the interstellar medium (ISM), thus regulating both star formation and supermassive black hole (SMBH) growth. We have undertaken a multi-band observing program aimed at obtaining a complete census of winds in a sample of WISE/SDSS selected hyper-luminous (WISSH) QSOs at z ≈ 2–4. We have analyzed the rest-frame optical (i.e. LBT/LUCI and VLT/SINFONI) and UV (i.e. SDSS) spectra of 18 randomly selected WISSH QSOs to measure the SMBH mass and study the properties of winds both in the narrow line region (NLR) and broad line region (BLR) traced by blueshifted/skewed [OIII] and CIV emission lines, respectively. These WISSH QSOs are powered by SMBH with masses > ∼ 109 M accreting at 0.4 < λEdd < 3.1. We have found the existence of two sub-populations of hyper-luminous Q...
X-raying the Winds of Luminous Active Galaxies
2009
We briefly describe some recent observational results, mainly at X-ray wavelengths, on the winds of luminous active galactic nuclei (AGNs). These winds likely play a significant role in galaxy feedback. Topics covered include (1) Relations between X-ray and UV absorption in Broad Absorption Line (BAL) and mini-BAL quasars; (2) X-ray absorption in radio-loud BAL quasars; and (3) Evidence for relativistic iron K BALs in the X-ray spectra of a few bright quasars. We also mention some key outstanding problems and prospects for future advances; e.g., with the International X-ray Observatory (IXO).
Monthly Notices of the Royal Astronomical Society, 2011
We present an analysis of the kinematics and excitation of the warm ionized gas in two obscured, powerful quasars at z 3.5 from the SWIRE survey, SWIRE J022513.90-043419.9 and SWIRE J022550.67-042142, based on imaging spectroscopy on the VLT. Line ratios in both targets are consistent with luminous narrow-line regions of AGN. SWIRE J022550.67-042142 has very broad (FWHM=2000 km s −1), spatially compact [OIII] line emission. SWIRE J022513.90-043419.9 is spatially resolved, has complex line profiles of Hβ and [OIII], including broad wings with blueshifts of up to −1500 km s −1 relative to the narrow [OIII]λ5007 component, and widths of up to FWHM=5000 km s −1. Estimating the systemic redshift from the narrow Hβ line, as is standard for AGN host galaxies, implies that a significant fraction of the molecular gas is blueshifted relative to the systemic velocity. Thus the molecular gas could be participating in the outflow. Significant fractions of the ionized and molecular gas reach velocities greater than the escape velocity. We compare empirical and modeling constraints for different energy injection mechanisms, such as merging, star formation, and momentum-driven AGN winds. We argue that the radio source is the most likely culprit, in spite of the sources rather modest radio power of 10 25 W Hz −1. Such a radio power is not uncommon for intense starburst galaxies at z∼2. We disucss these results in light of the co-evolution of AGN and their host galaxy.
Dust emission from quasars and quasar host galaxies
Monthly Notices of the Royal Astronomical Society, 1999
We test emission models of circumnuclear dust tori around quasars, at low and high redshifts, by using a large collection of photometric data for an unbiased sample of 120 optically selected objects with millimetric and submillimetric¯uxes, including new unpublished data. Under the assumption that the dust is heated by a point-like source with a power-law primary spectrum, as de®ned by the observed optical±ultraviolet continuum, we infer the basic model parameters, such as dust masses, temperature distributions and torus sizes, by numerically solving the radiative transfer equation in the dust distribution. In addition to the substantiated statistics, an essential improvement over previous analyses comes from the use of optical±ultraviolet data to constrain the primary illuminating continuum, which is needed to estimate dust temperatures and sizes. The dependences of the best-®tting parameters on luminosity and redshift are studied and the contribution of dust in the host galaxy to the observed¯uxes is brie¯y mentioned. This analysis constrains the properties of the enriched interstellar medium in the galaxies hosting the quasars. The dust abundance does not display appreciable trends as a function of redshift, from z. 1 to almost 5, and shows that at these early epochs dust and metals are at least as abundant as, and often more abundant than, they are in local Galactic counterparts. This evolutionary pattern is remarkably at variance with respect to what is expected for disc galaxies, like the Milky Way, slowly building metals during the whole Hubble time. It rather points in favour of a much more active phase of star formation at early epochs, probably related to the formation of massive spheroidal galaxies.
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.
Metal-enriched Outflows and Dusty Starburst in the Type II Quasar Q 1321+058
We present an analysis of the emission-line property and the broadband spectral energy distribution of the ultraluminous infrared Type II quasar Q 1321+058. The optical and ultraviolet emission lines show four distinct components: a LINER-like component at the systematic velocity, a heavily reddened H II-like component blueshifted by about 400 km s −1 , and two broad components blueshifted by about 400 km s −1 and 1900 km s −1 , respectively. The emissionline ratios suggest that broad components are produced in dense and α-enriched outflows with a metalicity of 3-5 Z ⊙ and a density of n H ∼ 10 7 cm −3 . The optical-UV continuum is dominated by stellar light and can be modeled with a young (< 1 Myr) plus an intermediate-age (0.5-0.8 Gyr) stellar populations. The near to mid-infrared light is dominated by hot and warm dust heated by the hidden quasar. We derive a star formation rate (SFR) of 300-500 M ⊙ yr −1 from the UV spectrum and far-infrared luminosity, which is two orders of magnitude larger than that indicated by reddening-uncorrected [O II] luminosity.