We obtained medium-resolution ultraviolet (UV) spectra between 1150 and 1450 Angstroms of the four UV-bright, infrared (IR)-luminous starburst galaxies IRAS F08339+6517, NGC 3256, NGC 6090, and NGC 7552 using the Cosmic Origins Spectrograph onboard the Hubble Space Telescope. The selected sightlines towards the starburst nuclei probe the properties of the recently formed massive stars and the physical conditions in the starburst-driven galactic superwinds. Despite being metal-rich and dusty, all four galaxies are strong Lyman-alpha emitters with equivalent widths ranging between 2 and 13 Angstroms. The UV spectra show strong P Cygni-type high-ionization features indicative of stellar winds and blueshifted low-ionization lines formed in the interstellar and circumgalactic medium. We detect outflowing gas with bulk velocities of about 400 km/s and maximum velocities of almost 900 km/s. These are among the highest values found in the local universe and comparable to outflow velocities found in luminous Lyman-break galaxies at intermediate and high redshift. The outflow velocities are unlikely to be high enough to cause escape of material from the galactic gravitational potential. However, the winds are significant for the evolution of the galaxies by transporting heavy elements from the starburst nuclei and enriching the galaxy halos. The derived mass outflow rates of ~100 Msol/yr are comparable to, or even higher than the star-formation rates. The outflows can quench star formation and ultimately regulate the starburst as has been suggested for high-redshift galaxies.
Physical Conditions in the Low-Ionization Component of Starburst Outflows: The Shape of Near-Ultraviolet and Optical Absorption-Line Troughs in Keck Spectra of ULIRGs
我们分析的物理条件，在低电离成分的星爆外流（在X射线中观察到的高电离风流体相比），基于新的凯克/LRIS光谱的部分解决吸收槽在近紫外和光学光谱的超铝红外Galerkin。大的速度宽度和蓝移存在于七，原子跃迁表明流出的气体内的宏观速度梯度。这些数据中的\mgII 2796、2803（和\feII 2587、2600）双峰线比重度混合的\nad 5892、98双峰线更好地约束气体运动学。\mgII 2796吸收槽的形状与2803 μ m处通常较弱的跃迁的形状相同，这要求两个跃迁在所有流出速度下都具有光学厚度。因此，在每一个速度下流出物所覆盖的银河系连续统的分数决定了这些吸收槽的形状。我们认为，速度偏移的最深的部分的槽，低电离气体的覆盖因子是接近统一的，反映了速度的外壳扫，星际气体在井喷的时候。在一个球形流出，我们表明，该壳的碎片膨胀缓慢相对于几何稀释，低电离气体的覆盖率随半径的增加而减小。因此，我们测量的覆盖因子随速度的增加而减少，可以解释为低电离外流加速的证据。我们还测量了四种气体的C_f（v），给出了流出气体密度的上限为3000 cm ~ 3，并讨论了质量流出速率的下限。
Broad emission-line outflows of active galactic nuclei (AGNs) have been proposed for many years but are very difficult to quantitatively study because of the coexistence of the gravitationally-bound and outflow emission. We present detailed analysis of a heavily reddened quasar, SDSS J000610.67+121501.2, whose normal ultraviolet (UV) broad emission lines (BELs) are heavily suppressed by the Dusty Torus as a natural "Coronagraph", thus the blueshifted BELs (BBELs) can be reliably measured. The physical properties of the emission-line outflows are derived as follows: ionization parameter $U \sim…
High-redshift quasars typically have their redshift determined from rest-frame ultraviolet (UV) emission lines. However, these lines, and more specifically the prominent C IV $λ1549$ emission line, are typically blueshifted yielding highly uncertain redshift estimates compared to redshifts determined from rest-frame optical emission lines. We present near-infrared spectroscopy of 18 luminous quasars at $2.15 < z < 3.70$ that allows us to obtain reliable systemic redshifts for these sources. Together with near-infrared spectroscopy of an archival sample of 44 quasars with comparable luminositie…
An analysis of ~19500 narrow (<200 km/s) CIV 1548.2,1550.8 absorbers in ~34000 Sloan Digital Sky Survey quasar spectra is presented. The statistics of the number of absorbers as a function of outflow-velocity shows that in approximately two-thirds of outflows, with multiple CIV absorbers present, absorbers are line-locked at the 500 km/s velocity separation of the CIV absorber doublet; appearing as 'triplets' in the quasar spectra. Line-locking is an observational signature of radiative line driving in outflowing material, where the successive shielding of 'clouds' of material in the outflow l…
We perform a systematic study of outflow in the narrow-line region (NLR) of active galactic nuclei (AGNs) at $z\sim0.4-0.8$ basing upon a large sample of $\sim900$ quasars at $z\sim 0.4-0.8$. The sample is extracted from the Sloan Digital Sky Survey by mainly requiring 1) the g-band magnitude is brighter than 19 magnitude; and 2) the [OIII]$\lambda5007$ emission line has a signal-to-noise ration larger than 30. Profiles of multiple emission lines are modeled by a sum of several Gaussian functions. The spectral analysis allows us to identify 1) a prevalence of both [OIII]$\lambda5007$ line blue…
The origin of outflow in narrow-line region (NLR) of active galactic nucleus (AGN) is studied in this paper by focusing on the relationship between the [\ion{O}{3}]$λ$5007 line profile and the hard X-ray (in a bandpass of 2-10 keV) emission from the central SMBH in type-I AGNs. A sample of 47 local X-ray selected type-I AGNs at $z<0.2$ is extracted from the 2XMMi/SDSS DR7 catalog that is originally crossmatched by Pineau et al. The X-ray luminosities in an energy band from 2 to 10keV of these luminous AGNs range from $10^{42}$ to $10^{44}\ \mathrm{erg\ s^{-1}}$. A joint spectral analysis is pe…
Context: Recent XMM-Newton observations have revealed that IRAS 17020+4544 is a very unusual example of black hole wind-produced feedback by a moderately luminous AGN in a spiral galaxy. Aims: Since the source is known for being a radio emitter, we investigated about the presence and the properties of a non-thermal component. Methods: We observed IRAS 17020+4544 with the Very Long Baseline Array at 5, 8, 15, and 24 GHz within a month of the 2014 XMM-Newton observations. We further analysed archival data taken in 2000 and 2012. Results: We detect the source at 5 GHz and on short baselines at 8 …
