ABSTRACT We perform Lyman- (Ly ) Monte-Carlo radiative transfer calculations on a suite of 2500 models of multiphase, outflowing media, which are characterized by 14 parameters. We focus on the Ly ...spectra emerging from these media and investigate which properties are dominant in shaping the emerging Ly profile. Multiphase models give rise to a wide variety of emerging spectra, including single-, double-, and triple-peaked spectra. We find that the dominant parameters in shaping the spectra include (i) the cloud covering factor, fc, which is in agreement with earlier studies, and (ii) the temperature and number density of residual H i in the hot ionized medium. We attempt to reproduce spectra emerging from multiphase models with "shell models" which are commonly used to fit observed Ly spectra, and investigate the connection between shell-model parameters and the physical parameters of the clumpy media. In shell models, the neutral hydrogen content of the shell is one of the key parameters controlling Ly radiative transfer. Because Ly spectra emerging from multiphase media depend much less on the neutral hydrogen content of the clumps, the shell-model parameters such as H i column density (but also shell velocity and dust content) are generally not well matched to the associated physical parameters of the clumpy media.
Lyman-
α
(Ly
α
) spectra provide insights into the small-scale structure and kinematics of neutral hydrogen (HI) within galaxies as well as the ionization state of the intergalactic medium (IGM). The ...former defines the intrinsic spectrum of a galaxy, which, in turn, is modified by the latter. These two effects are degenerate. Using the IllustrisTNG100 simulation, we studied the impact of the IGM on Ly
α
spectral shapes between
z
∼ 0 and 5. We computed the distribution of the expected Ly
α
peaks and of the peak asymmetry for different intrinsic spectra, redshifts, and large-scale environments. We find that the averaged transmission curves that are commonly applied give a misleading perception of the observed spectral properties. We show that the distributions of peak counts and asymmetry can lift the degeneracy between the intrinsic spectrum and IGM absorption. For example, we expect a significant number of triple-peaked Ly
α
spectra (up to 30% at
z
∼ 3) if the galaxies’ HI distribution become more porous at higher redshift, as predicted by cosmological simulations. We provide a public catalog of transmission curves for simulations and observations to allow for a more realistic IGM treatment in future studies.
ABSTRACT Galactic outflows have a multiphase nature making them challenging to model analytically. Many previous studies have tried to produce models that come closer to reality. In this work, we ...continue these efforts and describe the interaction of the hot wind fluid with multiple cold cloud populations, with their number density determined by different probability density functions. To do so, we introduced realistic cloud-wind interaction source terms and a time varying cooling area. We find that the model reproduces well results from small-scale hydrodynamic simulations, but exhibits a general destructive behaviour both for a single cloud population as well as multiple ones. We show that including multiple cloud populations can alter the evolution of the wind drastically. We also compare our model to observations and show that the differential acceleration of multiple clouds can lead to a non-negligible velocity ‘dispersion’ relevant for down-the-barrel studies. Furthermore, we compute the emitted cooling surface brightness and find it generally too faint to explain observed Lyman α haloes.
We quantify the directional dependence of the escape fraction of Lyman α (Lyα) and non-ionizing UV-continuum photons from a multiphase medium, and investigate whether there exist directional ...enhancements in the Lyα equivalent width (EW). Our multiphase medium consists of spherically symmetric distributions of cold, dusty clumps embedded within a hot dust-free medium. We focus on three models from the analysis presented by Laursen et al. We find that for a Lyα and UV-continuum point source, it is possible to find an EW boost
$b(\theta ,\phi ) > 5 \bar{b}$
in a few per cent of sight lines, where
$\bar{b}$
denotes the boost averaged over all photons. For spatially extended sources this directional dependence vanishes quickly when the size of the UV emitting region exceeds the mean distance between cold dusty clumps. Our analysis suggests that directional EW boosting can occur, and that this is mostly driven by reduced escape fractions of UV photons (which gives rise to UV-continuum ‘shadows’), and less due to an enhanced Lyα escape fraction (or beaming), in certain directions.
We present rest-frame ultraviolet and optical spectroscopy of the brightest lensed galaxy yet discovered, at redshift z = 2.4. The source reveals a characteristic triple-peaked Lyman α profile that ...has been predicted in various theoretical works, but to our knowledge has not been unambiguously observed previously. The feature is well fit by a superposition of two components: a double-peak profile emerging from substantial radiative transfer, and a narrow, central component resulting from directly escaping Lyman α photons, but it is poorly fit by either component alone. We demonstrate that the feature is unlikely to contain contamination from nearby sources, and that the central peak is unaffected by radiative transfer effects except for very slight absorption. The feature is detected at signal-to-noise ratios exceeding 80 per pixel at line center, and bears strong resemblance to synthetic profiles predicted by numerical models.
We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 + or - 0.33 (M sub(UV)=-17.0, low-mass (<, ~10 super(7)M sub(middo t in circle)), and compact (R sub(eff)= 62 pc) freshly ...star-forming galaxy at z= 3.1169 magnified (16x) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R= lambda /dlambda ~ 3000-7400). We measured C IV lambda 1548, 1550, He II lambda 1640, O IIIlambda 1661,1666, C IIIlambdalambda 1907,1909, Hbeta, OIIIlambdalambda 4959,5007 emission lines with <, ~ 50 km s super(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10 super(-19)-2 x 10 super(-18) erg s super(-1) cm super(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Lyalpha emission with Deltanured - blue) = 280 (+ or -7) km s super(-1) and de-lensed fluxes 2.4 sub((blue)) 8.5 sub((red)) x 10 super(-18) erg s super(-1) cm super(-2)(S/N = 38 sub((blue)) 110 sub((red))) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large OIIIlambda 5007/ OIIlambda 3727 > 10 ratio. We detect C IV lambda 1548,1550 resonant doublet in emission, each component with FWHM <, ~ 45 km s super(-1) and redshifted by +51(+ or -10) km s super(-1) relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV lambda 1548,1550 and He II lambda 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, beta =-2.95 + or - 0.20 (F sub(lambda)= lambda super(beta)), consistent with a dust-free and young <, ~20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H) < 7.8. We are witnessing an early episode of star formation in which a relatively low N sub(H I) and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space Telescope.
In spite of their conjectured importance for the Epoch of Reionization, the properties of low-mass galaxies are currently still very much under debate. In this article, we study the stellar and ...gaseous properties of faint, low-mass galaxies at z> 3. We observed the Frontier Fields cluster Abell S1063 with MUSE over a 2 arcmin super(2) field, and combined integral-field spectroscopy with gravitational lensing to perform a blind search for intrinsically faint Ly alpha emitters (LAEs). We determined in total the redshift of 172 galaxies of which 14 are lensed LAEs at z=3-6.1. We increased the number of spectroscopically-confirmed multiple-image families from 6 to 17 and updated our gravitational-lensing model accordingly. The lensing-corrected Ly alpha luminosities are with L sub(Ly alpha ) <, ~ 10 super(41.5) erg/s among the lowest for spectroscopically confirmed LAEs at any redshift. We used expanding gaseous shell models to fit the Ly alpha line profile, and find low column densities and expansion velocities. This is, to our knowledge, the first time that gaseous properties of such faint galaxies at z> ~ 3 are reported. We performed SED modelling to broadband photometry from the U band through the infrared to determine the stellar properties of these LAEs. The stellar masses are very low (10 super(6-8)M sub(middot in circle)), and are accompanied by very young ages of 1-100 Myr. The very high specific star-formation rates (~100 Gyr super(-1)) are characteristic of starburst galaxies, and we find that most galaxies will double their stellar mass in <, ~ 20 Myr. The UV-continuum slopes beta are low in our sample, with beta < -2 for all galaxies with Mlow * < 10 super(8)M sub(middot in circle). We conclude that our low-mass galaxies at 3 < z< 6 are forming stars at higher rates when correcting for stellar mass effects than seen locally or in more massive galaxies. The young stellar populations with high star-formation rates and low Hi column densities lead to continuum slopes and LyC-escape fractions expected for a scenario where low mass galaxies reionise the Universe.
We predict Lyman alpha (Ly alpha ) luminosity functions (LFs) of Ly alpha -selected galaxies (Ly alpha emitters, or LAEs) at z = 3-6 using the phenomenological model. This model combines observed ...UV-LFs of Lyman-break galaxies (LBGs, or drop-out galaxies), with constraints on their distribution of Ly alpha line strengths as a function of UV-luminosity and redshift. Our analysis shows that while Ly alpha LFs of LAEs are generally not Schechter functions, these provide a good description over the luminosity range of log sub(10)(L sub( alpha )/erg s super(-1)) = 41-44. Motivated by this result, we predict Schechter function parameters at z = 3-6. Our analysis further shows that (i) the faint-end slope of the Ly alpha LF is steeper than that of the UV-LF of LBGs, (with a median alpha sub(Ly alpha ) < -2.0 at z greater than or equal to 4), and (ii) a turnover in the Ly alpha LF of LAEs at Ly alpha luminosities 10 super(40) erg s super(-1) < L sub( alpha ) less than or equal to 10 super(41) erg s super(-1) may signal a flattening of UV-LF of LBGs at -12 > M sub(UV) > -14. We discuss the implications of these results -- which can be tested directly with upcoming surveys -- for the Epoch of Reionization.
ABSTRACT
We discovered a strongly lensed (μ ≳ 40) Ly α emission at z = 6.629 (S/N ≃ 18) in the MUSE Deep Lensed Field (MDLF) targeting the Hubble Frontier Field (HFF) galaxy cluster MACS J0416. ...Dedicated lensing simulations imply that the Ly α emitting region necessarily crosses the caustic. The arc-like shape of the Ly α extends 3 arcsec on the observed plane and is the result of two merged multiple images, each one with a de-lensed Ly α luminosity L ≲ 2.8 × 1040 erg s−1 arising from a confined region (≲150 pc effective radius). A spatially unresolved Hubble Space Telescope(HST) counterpart is barely detected at S/N ≃ 2 after stacking the near-infrared bands, corresponding to an observed (intrinsic) magnitude m1500 ≳ 30.8 (≳35.0). The inferred rest-frame Ly α equivalent width is EW0 > 1120 Å if the IGM transmission is TIGM < 0.5. The low luminosities and the extremely large Ly α EW0 match the case of a Population III (Pop III) star complex made of several dozens stars (∼104 M⊙) that irradiate an H ii region crossing the caustic. While the Ly α and stellar continuum are among the faintest ever observed at this redshift, the continuum and the Ly α emissions could be affected by differential magnification, possibly biasing the EW0 estimate. The aforementioned tentative HST detection tends to favour a large EW0, making such a faint Pop III candidate a key target for the James Webb Space Telescope and Extremely Large Telescopes.
We have discovered a 300 kpc-wide giant Lyman-
α
(Ly
α
) nebula centered on the massive galaxy group RO-1001 at
z
= 2.91 in the Cosmic Evolution Survey field. Keck Cosmic Web Imager observations ...reveal three cold gas filaments converging into the center of the potential well of its ∼4 × 10
13
M
⊙
dark matter halo, hosting 1200
M
⊙
yr
−1
of star formation as probed by Atacama Large Millimeter Array and NOrthern Extended Millimeter Array observations. The nebula morphological and kinematics properties and the prevalence of blueshifted components in the Ly
α
spectra are consistent with a scenario of gas accretion. The upper limits on active galactic nuclei activity and overall energetics favor gravity as the primary Ly
α
powering source and infall as the main source of gas flows to the system. Although interpretational difficulties remain, with outflows and likely also photoionization with ensuing recombination still playing a role, this finding provides arguably an ideal environment to quantitatively test models of cold gas accretion and galaxy feeding inside an actively star-forming massive halo at high redshift.
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