What is the contribution of mass, metals and energy from starburst galaxies to the Intergalactic Medium? Starburst galaxies drive galactic-scale outflows or "superwinds" that may be responsible for removing metals from galaxies and polluting the Intergalactic Medium (IGM). In the last decade tremendous progress was made in mapping cool entrained gas in superwinds through UV/optical imaging and absorption line spectroscopy. These studies demonstrated that superwinds are ubiquitous in galaxies forming stars at high surface densities and that the most powerful starbursts can drive outflows near escape velocity. Theoretical models of galaxy evolution have begun to incorporate superwinds, using various ad-hoc prescriptions based on our knowledge of the cool gas. However, these efforts are fundamentally impeded by our lack of information about the hot phase of these outflows. The hot X-ray emitting phase of a superwind contains the majority of its energy and newly-synthesized metals, and given its high specific energy and inefficient cooling it is also the component most likely escape from the galaxy's gravitational potential well. Knowledge of the chemical composition and velocity of the hot gas are crucial to assess the energy and chemical feedback from a starburst. A high priority for the next decade is to enable direct measurements to be made of the rates at which starburst galaxies of all masses eject gas, metals, and energy into the IGM. This will require a high sensitivity X-ray imaging spectrometer capable of measuring velocities in faint diffuse X-ray emission with a velocity accuracy of ~ 100 km/s. Such spectral resolution automatically allows detailed line-based plasma diagnostics, and thus composition, energetics and flow rates can be derived.
We investigate the large-scale influence of outflows from AGNs in enriching the IGM with metals in a cosmological context. We combine cosmological simulations of large scale structure formation with a detailed model of metal enrichment, in which outflows expand anisotropically along the direction of least resistance, distributing metals into the IGM. The metals carried by the outflows are generated by two separate stellar populations: stars located near the central AGN, and stars located in the greater galaxy. Using this algorithm, we performed a series of 5 simulations of the propagation of A…
Galactic outflows play a major role in the evolution of galaxies and the intergalactic medium (IGM). The energy deposited into the interstellar medium by supernovae and active galactic nuclei can accelerate the gas past the escape velocity, and eject it into the IGM. This will affect the subsequent evolution of the galaxy, by reducing or eliminating star formation, and quenching the accretion of matter onto the central AGN. Galactic outflows is the main process by which energy and processed interstellar matter is transported into the IGM. This affects the subsequent formation of other galaxies…
Galactic outflows can be powered either by nuclear starbursts (SB) or active galactic nuclei (AGN). It has been argued that extreme starbursts can power extreme outflows, without the need to invoke AGN feedback. However, contributions from past and/or hidden AGN activity cannot be ruled out. Here, we constrain the potential role of the central black hole in driving powerful outflows in starburst galaxies (with no sign of ongoing AGN activity). We examine whether the galactic outflows can be explained by AGN luminosity evolution in the framework of our AGN `radiative dusty feedback' scenario. W…
We present semi-analytical models of galactic outflows in high redshift galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal pressure alone may not sustain a large scale outflow in low mass galaxies (i.e $M\sim 10^8$~M$_\odot$), in the presence of supernovae (SNe) feedback with large mass loading. We show that inclusion of cosmic ray pressure allows outflow solutions even in these galaxies. In massive galaxies for the same energy efficiency, cosmic ray driven winds can propagate to larger distances compared to pure thermally driven winds. On an average gas in the cosmic…
We successfully detected a molecular outflow with a scale of 370-450 pc in the central region of the starburst galaxy NGC 3628 through deep CO(1-0) observations by using the Nobeyama Millimeter Array (NMA). The mass of the outflowing molecular gas is ~2.8x10^7 M_sun, and the outflow velocity is ~90(+/-10) km s^{-1}. The expansion timescale of the outflow is 3.3-6.8 Myr, and the molecular gas mass flow rate is 4.1-8.5 M_sun yr^{-1}. It requires mechanical energy of (1.8-2.8)x10^{54} erg to create this sub-kpc scale molecular outflow. In order to understand the evolution of the molecular outflow…
We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive ($M_{\rm halo}\gtrsim 10^{11}\,M_{\odot}$), low-redshift ($z\lesssim 1-2$) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. …
X-ray properties of hot interstellar gas in a starburst galaxy NGC 253 were investigated to gain a further understanding of starburst-driven outflow activity by XMM-Newton and Suzaku. Spectroscopic analysis for three regions of the galaxy characterized by multiwavelength observations was conducted. The hot gas was represented by two thin thermal plasmas with temperatures of kT ~0.2 and ~0.6 keV. Abundance ratios i.e., O/Fe, Ne/Fe, Mg/Fe and Si/Fe, are consistent between three regions, which suggests the common origin of the hot gas. The abundance patterns are consistent with those of type II s…
We propose a model of starburst--driven galactic outflows whose dynamics depends on both radiation and thermal pressure. Standard models of thermal pressure--driven winds fail to explain some key observations of outflows at low and high redshift galaxies. We discuss a scenario in which radiation pressure from massive stars in a stellar population drive a shell of gas and dust. Subsequent supernova (SN) explosions from the most massive stars in this population then drive stellar ejecta outward in a rarefied medium, making it collide with the radiation pressure driven shell. The collision impart…
We present Keck/LRIS-B spectra for a sample of ten AEGIS X-ray AGN host galaxies and thirteen post-starburst galaxies from SDSS and DEEP2 at 0.2<z<0.8 in order to investigate the presence, properties, and influence of outflowing galactic winds at intermediate redshifts. We focus on galaxies that either host a low-luminosity AGN or have recently had their star formation quenched to test whether these galaxies have winds of sufficient velocity to potentially clear gas from the galaxy. We find, using absorption features of Fe II, Mg II, and Mg I, that six of the ten (60%) X-ray AGN host galaxies …
We combine an analytic model for anisotropic outflows and galaxy formation with numerical simulations of large-scale structure and halo formation to study the impact of galactic outflows on the evolution of the IGM. We have simulated the evolution of a comoving volume (15 Mpc)^3 in the LCDM universe. We follow the formation of 20000-60000 galaxies and simulate the galactic outflows produced by these galaxies, for five outflow opening angles, alpha=60, 90, 120, 150, and 180 degrees (isotropic outflows). Anisotropic outflows follow the path of least resistance and thus travel preferentially into…
(Abridged) Star formation-driven outflows are a critical phenomenon in theoretical treatments of galaxy evolution, despite the limited ability of observations to trace them across cosmological timescales. If the strongest MgII absorption-line systems detected in the spectra of background quasars arise in such outflows, "ultra-strong" MgII (USMgII) absorbers would identify significant numbers of galactic winds over a huge baseline in cosmic time, in a manner independent of the luminous properties of the galaxy. To this end, we present the first detailed imaging and spectroscopic study of the fi…
Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the phenomenon, such as the molecular mass, speed and size of the outflows. We show that outflows triggered by OB associations, with $N_{OB}\ge 10^5$ (corresponding to a star formation rate (SFR)$\ge 1$ M$_{\odot}$ yr$^{-1}$ in the nuclear region), in a stratified disk with mid-plane density $n_0\sim 200\hbox{--}1000$ cm$^{-3}$ and scale height $z_0\ge 200 (n_0/10^2 \, {…
Recent well resolved numerical simulations of AGN feedback have shown that its effects on the host galaxy may be not only negative but also positive. In the late gas poor phase, AGN feedback blows the gas away and terminates star formation. However, in the gas-rich phase(s), AGN outflows trigger star formation by over-compressing cold dense gas and thus provide positive feedback on their hosts. In this paper we study this AGN-triggered starburst effect. We show that star formation rate in the burst increases until the star formation feedback counteracts locally the AGN outflow compression. Glo…
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 MgII and FeII resonance transitions with Doppler shifts of -200 to -300 km/s, indicating a cool gas outflow. Emission in MgII 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 Ly alpha transition in Lyman Break Galaxies. Further, the MgII emission is spatially resolved, and extends significantly beyond…
We present semi-analytical models for magnetisation of the void inter-galactic medium (IGM) by outflows from void galaxies. The number density of dark matter haloes in an under-dense region (i.e., void) is obtained using the excursion set method extended for such low density environment. The star formation in such haloes has been estimated, taking account of the negative feedback by supernovae. The galaxy formation/evolution model is tuned to provide the $r$-band luminosity function, the stellar mass function and also the color of void galaxies as obtained from recent observations. This star f…
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 Angst…
We present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive ($\rm M_* \sim 10^{11} M_{\odot}$), compact starburst galaxies at z = 0.4-0.7. We use data from Keck/NIRSPEC, SDSS, Gemini/GMOS, MMT, and Magellan/MagE to measure rest-frame optical and near-IR spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean $\rm Σ_{SFR} \sim 3000 \,M_{\odot} yr^{-1} kpc^{-2}$) and powerful galactic outflows (maximum speeds v$_{98} \sim$ 1000-3000 km s$^{-1}$). Our unique data set includes an ensemble of …
Neutral outflows have been detected in many ultraluminous infrared galaxies (ULIRGs) via the Na I D $λλ5890, 5896$ absorption-line doublet. For the first time, we have mapped and analyzed the 2-D kinematics of a cool neutral outflow in a ULIRG, F10565+2448, using the integral field unit (IFU) on Gemini North to observe the Na I D feature. At the same time we have mapped the ionized outflow with the [NII] and H$α$ emission lines. We find a systemic rotation curve that is consistent with the rotation of the molecular disk determined from previous CO observations. The absorption lines show eviden…
Spectropolarimetry results for the starburst galaxy M82 are presented. The optical emission lines of the filaments in the energetic outflow ("superwind") from the nuclear starburst region of M82 are substantially polarized. The H-alpha polarization degrees and angles measured by our study are consistent with previous narrowband imaging polarimetry data. The polarized emission lines are redshifted with respect to the emission lines in the total light and systemic motion of the galaxy. The emission line intensity ratios [NII]/H-alpha and [SII]/H-alpha in the polarized light are similar to those …
We analyze the physical conditions in the low-ionization component of starburst outflows (in contrast to the high-ionization wind fluid observed in X-rays), based on new Keck/LRIS spectroscopy of partially resolved absorption troughs in near-ultraviolet and optical spectra of Ultraluminous Infrared Galaxies. The large velocity width and blueshift present in seven, atomic transitions indicate a macroscopic velocity gradient within the outflowing gas. The \mgII 2796, 2803 (and \feII 2587, 2600) doublet lines in these data constrains the gas kinematics better than the heavily blended \nad 5892, 9…
We present the detection of Ly-alpha, [OIII] and H-alpha emission associated with an extremely strong DLA system (N(HI) = 10^22.10 cm^-2) at z=2.207 towards the quasar SDSS J113520-001053. This is the largest HI column density ever measured along a QSO line of sight, though typical of what is seen in GRB-DLAs. This absorption system also classifies as ultrastrong MgII system with W2796_r=3.6 A. The mean metallicity of the gas ([Zn/H]=-1.1) and dust depletion factors ([Zn/Fe]=0.72, [Zn/Cr]=0.49) are consistent with (and only marginally larger than) the mean values found in the general QSO-DLA p…
In the near future, measurements of metal absorption features in the intergalactic medium (IGM) will become an important constraint on models of the formation and evolution of the earliest galaxies, the properties of the first stars, and the reionization and enrichment of the IGM. The first measurement of a metal abundance in the IGM at a redshift approaching the epoch of reionization already offers intriguing hints. Between z=5.8 and 4.7 (a 0.3 Gyr interval only 1 Gyr after the big bang), the measured density of CIV absorbers in the IGM increased by a factor of ~ 3.5 (Ryan-Weber et al. 2009; …
We study the properties of massive, galactic-scale outflows of molecular gas and investigate their impact on galaxy evolution. We present new IRAM PdBI CO(1-0) observations of local ULIRGs and QSO hosts: clear signature of massive and energetic molecular outflows, extending on kpc scales, is found in the CO(1-0) kinematics of four out of seven sources, with measured outflow rates of several 100 Msun/yr. We combine these new observations with data from the literature, and explore the nature and origin of massive molecular outflows within an extended sample of 19 local galaxies. We find that sta…
Magnetic fields are a good tracer for gas compression by shock waves, which can be caused by interaction of star-formation driven outflows from individual star formation sites as described in the chimney model. We study the magnetic field structure in the central part of the nuclear starburst galaxy NGC 253 with spatial resolutions between 40 and 150 pc to detect any filamentary emission associated with the nuclear outflow. New VLA observations at 3 cm with 7.5" resolution were combined with archive data at 20 and 6 cm. We find filamentary radio continuum emission in a geometrical distribution…
An important property of star-forming galaxies at z~1-2 is the high local star-formation intensities they maintain over tens of kiloparsecs at levels that are only observed in the nearby Universe in the most powerful nuclear starbursts. To investigate how these high star-formation intensities affect the warm ionized medium, we present an analysis of the average spectra of about 50 such galaxies at z~1.2-2.6 and of subsamples selected according to their local and global star-formation intensity. Stacking allows us to probe relatively weak lines like [SII]λλ6716,6731 and [OI]λ6300, which are tra…
Post-Starburst Quasars (PSQs) are hypothesized to represent a stage in the evolution of massive galaxies in which the star formation has been recently quenched due to the feedback of the nuclear activity. In this paper our goal is to test this scenario with a resolved stellar population study of the PSQ J0210-0903, as well as of its emitting gas kinematics and excitation. We have used optical Integral Field Spectroscopy obtained with the Gemini GMOS instrument at a velocity resolution of ~120 km/s and spatial resolution of ~0.5 kpc. We find that old stars dominate the luminosity (at 4700 Å) in…
We model the latest HST WFPC3/IR observations of > 100 galaxies at redshifts z=7-8 in terms of a hierarchical galaxy formation model with starburst activity. Our model provides a distribution of UV luminosities per dark matter halo of a given mass and a natural explanation for the fraction of halos hosting galaxies. The observed luminosity function is best fit with a minimum halo mass per galaxy of 10^{9.4+0.3-0.9} Msun, corresponding to a virial temperature of 10^{4.9+0.2-0.7} K. Extrapolating to faint, undetected galaxies, the total production rate of ionizing radiation depends critically on…
We study the effects of galaxy formation physics on the magnetization of the intergalactic medium (IGM) using the IllustrisTNG simulations. We demonstrate that large-scale regions affected by the outflows from galaxies and clusters contain magnetic fields that are several orders of magnitude stronger than in unaffected regions with the same electron density. Moreover, like magnetic fields amplified inside galaxies, these magnetic fields do not depend on the primordial seed, i.e. the adopted initial conditions for magnetic field strength. We study the volume filling fraction of these strong fie…
We present a spectroscopic catalogue of 40 luminous starburst galaxies at z=0.7--1.7 (median z=1.3). 19 of these are submillimetre galaxies (SMGs) and 21 are submillimetre-faint radio galaxies (SFRGs). This sample helps to fill in the redshift desert at z=1.2--1.7 in previous studies as well as probing a lower luminosity population of galaxies. Radio fluxes are used to determine star-formation rates for our sample which range from around 50 to 500 M$_\odot$ yr$^{-1}$ and are generally lower than those in z$\sim$2 SMGs. We identify nebular [OII] 3727 emission in the rest-UV spectra and use the …
The next generation of telescopes aim to directly observe the first generation of galaxies that initiated the reionization process in our Universe. The Lyman Alpha (Lya) emission line is robustly predicted to be the most prominent intrinsic spectral feature of these galaxies, making it an ideal target to search for and study high redshift galaxies. Unfortunately the large Gunn-Peterson optical depth of the surrounding neutral intergalactic medium (IGM) is thought to render this line extremely difficult to detect prior to reionization. In this paper we demonstrate that the radiative transfer ef…
Using Lyα emission line as a tracer of high redshift star forming galaxies, hundreds of Lyα emission line galaxies (LAEs) at z > 5 have been detected. These LAEs are considered to be low mass young galaxies, critical to the reionization of the universe and the metal enrichment of circumgalactic medium (CGM) and intergalactic medium (IGM). It is assumed that outflows in LAEs can help ionizing photons and Lyα photons escape out of galaxies. However we still know little about the outflows in high redshifts LAEs due to observational difficulties, especially at redshift > 5. Models of Lyα radiative…
IGM metal absorption lines observed in z>6 spectra offer the opportunity to probe early feedback processes, the nature of enriching sources, and the topology of reionization. We run high-resolution cosmological simulations including galactic outflows to study the observability and physical properties of 5 ions (C II, C IV, O I, Si II, Si IV) in absorption between z=8->5. We apply three cases for ionization conditions: Fully neutral, fully reionized, and a patchy model based on the flux from the nearest galaxy. We find that our simulations broadly fit available z~5-6 IGM metal-line data, althou…
The under-abundance of very massive galaxies in the universe is frequently attributed to the effect of galactic winds. Although ionized galactic winds are readily observable most of the expelled mass is likely in cooler atomic and molecular phases. Expanding molecular shells observed in starburst systems such as NGC 253 and M 82 may facilitate the entrainment of molecular gas in the wind. While shell properties are well constrained, determining the amount of outflowing gas emerging from such shells and the connection between this gas and the ionized wind requires spatial resolution <100 pc cou…
We performed spectral analysis of Suzaku data of the galactic disk and outflow regions of the starburst galaxy M82. Thermal modeling of the central disk regions requires at least three temperature components. The Ly$β$ line fluxes of O VIII and Ne X exceed those expected from a plasma in collisional ionization equilibrium. The ratios of Ly$β$/Ly$α$ lines for O VIII and Ne X are higher than those of collisional ionization equilibrium, which may be caused by the process of charge exchange. In the outflow wind region, the spectra are well reproduced with two-temperature thermal models, and we hav…
NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows. Observations were performed with the adaptive optics near infrared integral field spectrograph SINFONI on the VLT, complemented by longslit observations with ISAAC on the VLT, as well as N- and Q-band data from the Spitzer archive. The spatial and spectral resolutions of the SINFONI data are 50 pc and 83 km/s, respective…
We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters,which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well, or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N-Body/Smooth Particle Hydrodynamics simulations of galactic winds using the GADGET-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration i…
The next generation of telescopes aim to directly observe the first generation of galaxies that initiated the reionization process in our Universe. The Lyman Alpha (Lya) emission line is robustly predicted to be the most prominent intrinsic spectral feature of these galaxies, making it an ideal target to search for and study high-redshift galaxies. I briefly discuss why Lya emitting galaxies (LAEs) provide a good probe of the intergalactic medium (IGM) during the Epoch of Reionization (EoR). I argue that if we wish to fully exploit LAEs as a probe of the EoR, it is important to understand what…
Mass outflows driven by stars and active galactic nuclei are a key element in many current models of galaxy evolution. They may produce the observed black hole-galaxy mass relation and regulate and quench both star formation in the host galaxy and black hole accretion. However, observational evidence of such feedback processes through outflows of the bulk of the star forming molecular gas is still scarce. Here we report the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key proj…
Strong bursts of star formation in galaxies may be triggered either by internal or external mechanisms. We study the distribution and kinematics of the HI gas in the outer regions of 18 nearby starburst dwarf galaxies, that have accurate star-formation histories from HST observations of resolved stellar populations. We find that starburst dwarfs show a variety of HI morphologies, ranging from heavily disturbed HI distributions with major asymmetries, long filaments, and/or HI-stellar offsets, to lopsided HI distributions with minor asymmetries. We quantify the outer HI asymmetry for both our s…
ALMA observations have revealed that many high redshift galaxies are surrounded by extended (10-15 kpc) [CII]-emitting halos which are not predicted by even the most advanced zoom-in simulations. Using a semi-analytical model, in a previous work we suggested that such halos are produced by starburst-driven, catastrophically cooling outflows. Here, we further improve the model and compare its predictions with data from 7 star-forming ($10\lesssim \rm SFR/ M_\odot \rm yr^{-1}<100$) galaxies at z=4-6, observed in the ALPINE survey. We find that (a) detected [CII] halos are a natural by-product of…
We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of 9 star-forming ($\rm SFR=31\pm 20~M_{\odot}~yr^{-1}$) $z\sim 5.5$ galaxies for which the [CII]158$μ$m line has been previously obtained with ALMA. We first fit each line with a Gaussian function and compute the residuals by subtracting the best fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterised by a flux excess of $\sim 0.5$ mJy extended over $\sim 1000$ km~s$^{-1}$. Although we cannot exclude that …
Tracing ionized gas kinematics in Lyman-Break Analogs. Implications for star formation compactness and outflow properties
Universidad de La Serena（拉塞雷纳大学）；Instituto de Astrofísica de Andalucía (CSIC)（安达卢西亚天体物理研究所）；Centro de Estudios de Física del Cosmos de Aragón (CEFCA)（阿拉贡宇宙物理学研究中心）；INAF - Osservatorio Astronomico di Roma（意大利国家天文台罗马天文台）；Michigan Institute for Data Science, University of Michigan（密歇根大学数据科学研究所）
