We present the first robust detection of HI 21 cm emission in the blue compact galaxy Haro 11 using the 100m Robert C. Byrd Green Bank Telescope (GBT). Haro 11 is a luminous blue compact galaxy with emission in both Lyman Alpha and the Lyman continuum. We detect (5.1 $\pm$ 0.7 $\times$10$^8$) M$_{\odot}$ of HI gas at an assumed distance of 88 Mpc, making this galaxy HI deficient compared to other local galaxies with similar optical properties. Given this small HI mass, Haro 11 has an elevated M$_{H2}$/M$_{HI}$ ratio and a very low gas fraction compared to most local galaxies, and contains twice as much mass in ionized hydrogen as in neutral hydrogen. The HI emission has a linewidth of 71 kms$^{-1}$ and is offset 60 kms$^{-1}$ redward of the optical line center. It is undergoing a starburst after a recent merger which has elevated the star formation rate, and will deplete the gas supply in $<$ 0.2 Gyr. Although this starburst has elevated the SFR compared to galaxies with similar HI masses and linewidths, Haro 11 matches a trend of lower gas fractions toward higher star formation rates and is below the general trend of increasing HI mass with increasing luminosity. Taken together, our results paint Haro 11 as a standard low-mass galaxy that is undergoing an unusually efficient star formation episode.
Star forming galaxies are believed to be a major source of Lyman Continuum (LyC) radiation responsible for reionizing the early Universe. Direct observations of escaping ionizing radiation have however been few and with low escape fractions. In the local Universe, only ~10 emitters have been observed, with typical escape fractions of a few percent. The mechanisms regulating this escape need to be strongly evolving with redshift in order to account for the Epoch of Reionization. Gas content and star formation feedback are among the main suspects, known to both regulate neutral gas coverage and …
Understanding the escape of ionizing (Lyman continuum) photons from galaxies is vital for determining how galaxies contributed to reionization in the early universe. While directly detecting Lyman continuum from high redshift galaxies is impossible due to the intergalactic medium, low redshift galaxies in principle offer this possibility, but requirie observations from space. The first local galaxy for which Lyman continuum escape was found is Haro11 , a luminous blue compact galaxy at z=0.02, where observations with the FUSE satellite revealed an escape fraction of 3.3 %. However the FUSE ape…
Identifying the mechanism by which high energy Lyman continuum (LyC) photons escaped from early galaxies is one of the most pressing questions in cosmic evolution. Haro 11 is the best known local LyC leaking galaxy, providing an important opportunity to test our understanding of LyC escape. The observed LyC emission in this galaxy presumably originates from one of the three bright, photoionizing knots known as A, B, and C. It is known that Knot C has strong Ly$α$ emission, and Knot B hosts an unusually bright ultraluminous X-ray source, which may be a low-luminosity AGN. To clarify the LyC sou…
Lyman continuum and line emission are thought to be important agents in the reionization of the early universe. Haro 11 is a rare example of a local galaxy in which Ly$α$ and continuum emission have escaped without being absorbed or scattered by ambient gas and dust, potentially as a consequence of feedback from its X-ray sources. We build on our previous Chandra analysis of Haro 11 by analyzing three new observations. Our subpixel spatial analysis reveals that the two previously known X-ray sources are each better modelled as ensembles of at least 2 unresolved point sources. The spatial varia…
Radiation hydrodynamic simulation of the Haro 11 galaxy: the escape of LyC and Ly$α$ in a dwarf galaxy merger
Oskar Klein Centre, Department of Astronomy, Stockholm University（斯德哥尔摩大学天文学系奥斯克·克莱因中心）；Centre de Recherche Astrophysique de Lyon UMR5574, Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS（里昂天体物理研究中心）；Lund Observatory, Division of Astrophysics, Department of Physics, Lund University（隆德大学物理系天体物理学部隆德天文台）
We perform Lyman-alpha radiative transfer calculations for reproducing Lyman-alpha properties of star-forming galaxies at high redshifts. We model a galaxy as a halo in which the density distributions of Lyman-alpha sources and H I plus dust medium are described with exponential functions. We also consider an outflow of the medium that represents a momentum-driven wind in a gravitational potential well. We successfully reproduce both the spectra and the surface brightness profiles of eight star-forming galaxies at z =3-6 observed with MUSE using this outflowing halo model with Lyman-alpha scat…
The leakage of Lyman continuum photons from star forming galaxies is an elusive parameter. When observed, it provides a wealth of information on star formation in galaxies and the geometry of the interstellar medium, and puts constraints on the role of star forming galaxies in the reionization of the universe. H-alpha-selected galaxies at z~2 trace the highest star formation population at the peak of cosmic star formation history, providing a base for directly measuring Lyman continuum escape. Here we present this method, and highlight its benefits as well as caveats. We also use the method on…
We present the results of a stellar-population analysis of Lyman-alpha emitting galaxies (LAES) in GOODS-N at 1.9 < z < 3.5 spectroscopically identified by the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We provide a method for connecting emission-line detections from the blind spectroscopic survey to imaging counterparts, a crucial tool needed as HETDEX builds a massive database of ~1 million Lyman-alpha detections. Using photometric data spanning as many as 11 filters covering 0.4-4.5 microns from the Hubble and Spitzer Space Telescopes, we study the objects' global properties an…
We have used the capability of the MUSE instrument to explore the impact of stellar feedback at large scales in Haro 11, a galaxy under extreme starburst condition and one of the first galaxies where Lyman continuum (LyC) has been detected. Using Ha, [OIII] and [OI] emission lines from deep MUSE observations, we have constructed a sequence of velocity-dependent maps of the Ha emission, the state of the ionised gas and a tracer of fast shocks. These allowed us to investigate the ionisation structure of the galaxy in 50 kms^2 bins over a velocity range of -400 to 350 kms. The ionised gas in Haro…
Bright quasars, observed when the Universe was less than one billion years old (z>5.5), are known to host massive black holes (~10$^{9}$ M$_{\odot}$), and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high redshift quasars. However, observations based on the detection of Lyman Break Galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are selected through broad-band filters only. To circumvent such uncertainties, we here p…
Recent studies have revealed intense UV metal emission lines in a modest sample of z>7 Lyman-alpha emitters, indicating a hard ionizing spectrum is present. If such high ionization features are shown to be common, it may indicate that extreme radiation fields play a role in regulating the visibility of Lyman-alpha in the reionization era. Here we present deep near-infrared spectra of seven galaxies with Lyman-alpha emission at 5.4<z<8.7 (including a newly-confirmed lensed galaxy at z=6.031) and three bright z>7 photometric targets. In nine sources we do not detect UV metal lines. However in th…
We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum(LyC) emitter at low redshift -- the compact, low-metallicity, star-forming galaxy J1154+2443 -- with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Lya and CIII] 1909 emission, as well as OIII] 1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(CIII])$=11.7 \pm 2.9 Å$ rest-frame), although their equivalent widths should be reduced due to the loss of ionizing phot…
The stellar content of young massive star clusters emit large amounts of Lyman continuum photons and inject momentum into the inter stellar medium (ISM) by the strong stellar winds of the most massive stars in the cluster. When the most massive stars explode as supernovae, large amounts of mechanical energy are injected in the ISM. A detailed study of the ISM around these massive cluster provides insights on the effect of cluster feedback. We present high quality integral field spectroscopy taken with VLT/MUSE of two starburst galaxies: ESO 338-IG04 and Haro 11. Both galaxies contain a signifi…
We have studied high mass X-ray binary (HMXB) populations within two low-metallicity, starburst galaxies, Haro 11 and VV 114. These galaxies serve as analogs to high-redshift (z>2) Lyman break galaxies, and within the larger sample of Lyman break analogs (LBAs) are sufficiently nearby (<87 Mpc) to be spatially-resolved by Chandra. Previous studies of the X-ray emission in LBAs have found that the 2-10 keV luminosity per star formation rate (SFR) in these galaxies is elevated, potentially because of their low metallicities (12+log[O/H]= 8.3-8.4). Theoretically, the progenitors of XRBs forming i…
We use high quality VLT/MUSE data to study the kinematics and the ionized gas properties of Haro 11, a well known starburst merger system and the closest confirmed Lyman continuum leaking galaxy. We present results from integrated line maps, and from maps in three velocity bins comprising the blueshifted, systemic and redshifted emission. The kinematic analysis reveals complex velocities resulting from the interplay of virial motions and momentum feedback. Star formation happens intensively in three compact knots (knots A, B and C), but one, knot C, dominates the energy released in supernovae.…
Using the Space Telescope Imaging Spectrograph, we have obtained ultraviolet (UV) spectra from $\sim 1200$ to 2000 Å of known Lyman continuum (LyC) emitting galaxies at low redshift ($z \sim 0.3-0.4$) with varying absolute LyC escape fractions (fesc $\sim 0.01 - 0.72$). Our observations include in particular the galaxy J1243+4646, which has the highest known LyC escape fraction at low redshift. While all galaxies are known Lyman alpha emitters, we consistently detect an inventory of additional emission lines, including CIV 1550, HeII 1640, OIII] 1666, and CIII] 1909, whose origin is presumably…
We have obtained K-band spectra at R~5,000 and angular resolution 0.3" of a section of the Herbig-Haro 7 (HH7) bow shock, using the Near-Infrared Integral Field Spectrograph at Gemini North. Present in the portion of the data cube corresponding to the brightest part of the bow shock are emission lines of H2 with upper state energies ranging from ~6,000 K up to the dissociation energy of H2, ~50,000 K. Because of low signal-to-noise ratios, the highest excitation lines cannot be easily seen elsewhere in the observed region. However, excitation temperatures, measured throughout much of the obser…
Chandra observations of the nearby, candidate Lyman-continuum (LyC) emitting galaxy Tol 0440-381 show brightening of an X-ray source by at least a factor of 4 to a luminosity of 1.6E40 erg/s over 3.8~days. The X-ray emission likely arises from either a low-luminosity AGN or an ultraluminous X-ray source. The properties of the X-ray source are similar to those found in Haro 11 and Tololo 1247-232, the only other LyC-emitting galaxies that have been resolved in X-rays. All three galaxies host luminous, variable, and hard spectrum X-ray sources that are likely accretion-powered. Accretion onto co…
Chandra observations of the nearby, Lyman-continuum (LyC) emitting galaxy Tol 1247-232 resolve the X-ray emission and show that it is dominated by a point-like source with a hard spectrum ($Γ= 1.6 \pm 0.5$) and a high luminosity ($(9 \pm 2) \times 10^{40} \rm \, erg \, s^{-1}$). Comparison with an earlier XMM-Newton observation shows flux variation of a factor of 2. Hence the X-ray emission likely arises from an accreting X-ray source: a low-luminosity AGN or one or a few X-ray binaries. The Chandra X-ray source is similar to the point-like, hard spectrum ($Γ= 1.2 \pm 0.2$), high luminosity ($…
The processes allowing the escape of ionizing photons from galaxies into the intergalactic medium are poorly known. To understand how Lyman continuum (LyC) photons escape galaxies, we constrain the HI covering fractions and column densities using ultraviolet HI and metal absorption lines of 18 star-forming galaxies which have Lyman series observations. Nine of these galaxies are confirmed LyC emitters. We fit the stellar continuum, dust attenuation, metal, and HI properties to consistently determine the UV attenuation, as well as the column densities and covering factors of neutral hydrogen an…
Neutral diffuse intergalactic gas that existed during the Epoch of Reionization (EoR) suppresses Lyman Alpha (Lya) flux emitted by background galaxies. In this chapter I summarise the increasing observational support for the claim that Lya photons emitted by galaxies at z>6 are suppressed by intervening HI gas. I describe key physical processes that affect Lya transfer during the EoR. I argue that in spite of the uncertainties associated with this complex multiscale problem, the data on Lya emitting galaxies at z=0-6 strongly suggests that the observed reduction in Lya flux from galaxies at z>…
Understanding Ly$α$ emitting galaxies (LAEs) can be a key to reveal cosmic reionization and galaxy formation in the early Universe. Based on halo merger trees and Ly$α$ radiation transfer calculations, we model redshift evolution of LAEs and their observational properties at $z \ge 6$. We consider ionized bubbles associated with individual LAEs and IGM transmission of Ly$α$ photons. We find that Ly$α$ luminosity tightly correlates with halo mass and stellar mass, while the relation with star formation rate has a large dispersion. Comparing our models with the observed luminosity function by Ko…
Star-forming Compact Dwarf Galaxies (CDGs) resemble the expected pristine conditions of the first galaxies in the Universe and are the best systems to test models on primordial galaxy formation and evolution. Here we report on one of such CDGs, Tololo 1214-277, which presents a broad, single peaked, highly symmetric Ly$α$ emission line that had evaded theoretical interpretation so far. In this paper we reproduce for the first time these line features with two different physically motivated kinematic models: an interstellar medium composed by outflowing clumps with random motions and an homogen…
X-ray binaries may have helped reionize the early Universe by enabling Lyman continuum escape. We analyzed a set of 8 local galaxies that are potential Lyman leaking galaxies, identified by a blue color and weak emission lines, using Chandra X-ray observations. Five of the galaxies feature X-ray sources, while three galaxies are not significantly detected in X-rays. X-ray luminosities were found for the galaxies and X-ray sources. Four of the galaxies have elevated X-ray luminosity versus what would be expected based on star formation rate and metallicity. The presence of detected X-ray source…
We report the discovery of J0121+0025, an extremely luminous and young star-forming galaxy (M_UV = -24.11, log[L_Lya / erg s^-1] = 43.8) at z = 3.244 showing copious Lyman continuum (LyC) leakage (f_esc,abs ~ 40%). High signal-to-noise ratio rest-frame UV spectroscopy with the Gran Telescopio Canarias reveals a high significance (7.9 sigma) emission below the Lyman limit (< 912A), with a flux density level f_900A = 0.78 +/- 0.10 uJy, and strong P-Cygni in wind lines of OVI 1033A, NV 1240A and CIV 1550A that are indicative of a young age of the starburst (<10 Myr). The spectrum is rich in stell…
With a total integration time of 168 hours and a narrowband (NB) filter tuned to Lyman alpha at z = 8.8, the UltraVISTA survey has set out to find some of the most distant galaxies, on the verge of the Epoch of Reionization. Previous calculations of the expected number of detected Lya-emitting galaxies (LAEs) at this redshift did not explicitly take into account the radiative transfer (RT) of Lya. In this work we combine a theoretical model for the halo mass function with numerical results from high-res cosmological hydrosimulations with LyC+Lya RT, assessing the visibility of LAEs residing in…
Quasar proximity zones at $z>5.5$ correspond to over-dense and over-ionized environments. Galaxies found inside proximity zones can therefore display features which would otherwise be masked by absorption in the IGM. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three `proximate Lyman-$α$ emitters' (LAEs) within the proximity zone of quasar J0836 at $z=5.802$ (\textit{Aerith A, B} and \textit{C}). \textit{Aerith A}, located behind the quasar with an impact parameter $D_\perp = 278$ pkpc, provides the first detection of a Lyman-$α$ transverse p…
Spectroscopic observations of massive $z>7$ galaxies selected to have extremely large [OIII]+H$β$ equivalent width (EW $\sim1500$ Å) have recently revealed large Ly$α$ detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly$α$ at redshifts where the IGM is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly$α$ in galaxies with similar [OIII]+H$β$ EWs at $z\simeq2-3$. At these redshifts, the IGM is highly ionized, allowin…
We present semi-analytical models of high redshift Lyman-α emitters (LAEs) in order to constrain the star formation efficiency in those galaxies. Our supernova feedback induced star formation model along with Sheth-Tormman halo mass function correctly reproduces the shape, amplitude and the redshift evolution of UV and Lyman-α luminosity functions of LAEs in the redshift range z = 2 to 7.3. We show that the fraction of Lyman-α emitting galaxies increases with increasing redshifts reaching to unity just after the reionisation. However, we show that star formation efficiency in those LAEs does n…
The Ly$α$ emission line is one of the main observables of galaxies at high redshift, but its output depends strongly on the neutral gas distribution and kinematics around the star-forming regions where UV photons are produced. We present observations of Ly$α$ and 21-cm HI emission at comparable scales with the goal to qualitatively investigate how the neutral interstellar medium (ISM) properties impact Ly$α$ transfer in galaxies. We have observed 21-cm HI at the highest angular resolution possible (~ 3" beam) with the VLA in two local galaxies from the Lyman Alpha Reference Sample. We contrast…
HETDEX: Star Formation Stochasticity Diagram of Lyman Alpha Emitting Galaxies at Cosmic Noon Confirms Three Archetypes
Rutgers, the State University of New Jersey（新泽西州立罗格斯大学）；School of Natural Sciences, Institute for Advanced Study（高等研究院自然科学学院）；Columbia University（哥伦比亚大学）；New York City College of Technology（纽约市立技术学院）；University of Maryland Baltimore County（马里兰大学巴尔的摩县分校）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/GSFC空间科学与探索技术中心）；Purdue University（普渡大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；The Pennsylvania State University（宾夕法尼亚州立大学）
We study the link between galaxies and HI-selected absorption systems at z~3-4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field pectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\rm N_{\rm HI}\gtrsim 10^{16.5}~\rm cm^{-2}$. We identify 127 Ly$α$ emitting galaxies (LAEs) around the absorbers, corresponding to a detection rate of 82$\pm$16 per cent. The luminosity function of these LAEs is approximately 5 times higher in normalization than the field population and we detect a significant clustering of gal…
We present the first results of our pilot study of 8 photometrically selected Lyman continuum (LyC) emitting galaxy candidates from the COSMOS field and focus on their optical emission line ratios. Observations were performed in the H and K bands using the Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) instrument at the Keck Observatory, targeting the [OII], H$β$, and [OIII] emission lines. We find that photometrically selected LyC emitting galaxy candidates have high ionization parameters, based on their high [OIII]/[OII] ratios (O32), with an average ratio for our sample of 2.…
The new era of Lyman alpha emitters (LAEs): Typical star formation histories of LAEs in the ILLUSTRIS simulation
Universidad Central de Chile（智利中央大学）；Universidad de La Serena（拉塞雷纳大学）；Universidad Andrés Bello（安德烈斯贝洛大学）；Rutgers, the State University of New Jersey（新泽西州立罗格斯大学）；Institute for Advanced Study, Princeton（普林斯顿高等研究院）；Purdue University（普渡大学）
Probing the Nature of Lyman Continuum Emitting and Low-metallicity Galaxies Using the SKA
The NSF-Simons AI Institute for Cosmic Origins（NSF-Simons 宇宙起源人工智能研究所）；CNRS, IRAP（法国国家科学研究中心，天体物理学研究所在图卢兹）；Ecole Polytechnique Federale de Lausanne (EPFL)（洛桑联邦理工学院）
We report the discovery of a double-peaked Lyman-alpha profile in a galaxy at $z=6.803$, A370p\_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman-$α$ profile ($Δv=101_{-19}^{+38} (\pm48)\,\text{km s}^{-1}$) suggests an extremely high escape fraction of ionising photons $> 59(51)\% (2σ)$. The spectral energy distribution indicates a young ($50$ Myr), star-forming ($12\pm 6 \, \rm{M}_\odot \rm{yr}^{-1}$) galaxy with an IRAC excess implying strong [OIII]+H$β$ emission. On the basis of the high escape fraction measured, we demonstr…
