19 research outputs found
The MUSE Hubble Ultra Deep Field Survey X. Ly Equivalent Widths at
We present rest-frame Ly equivalent widths (EW) of 417 Ly
emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the
Very Large Telescope (VLT) at in the Hubble Ultra Deep Field.
Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST)
photometry data, we carefully measured EW values taking into account extended
Ly emission and UV continuum slopes (). Our LAEs reach
unprecedented depths, both in Ly luminosities and UV absolute
magnitudes, from log(/erg s) 41.0 to 43.0 and
from Muv -16 to -21 (0.01-1.0 ). The EW values span the
range of 5 to 240 \AA\ or larger, and their distribution can be well
fitted by an exponential law exp(EW/). Owing to
the high dynamic range in Muv, we find that the scale factor, ,
depends on Muv in the sense that including fainter Muv objects increases
, i.e., the Ando effect. The results indicate that selection
functions affect the EW scale factor. Taking these effects into account, we
find that our values are consistent with those in the literature
within uncertainties at at a given threshold of Muv
and . Interestingly, we find 12 objects with EW \AA\
above uncertainties. Two of these 12 LAEs show signatures of merger
or AGN activity: the weak CIV emission line. For the remaining
10 very large EW LAEs, we find that the EW values can be reproduced by young
stellar ages ( Myr) and low metallicities ( ). Otherwise, at least part of the Ly emission in these LAEs
needs to arise from anisotropic radiative transfer effects, fluorescence by
hidden AGN or quasi-stellar object activity, or gravitational cooling.Comment: 22 pages, 12 figures, 9 tables, accepted for publication in A&A (MUSE
UDF Series Paper X
The MUSE-Wide survey: A measurement of the Ly emitting fraction among galaxies
We present a measurement of the fraction of Lyman (Ly)
emitters () amongst HST continuum-selected galaxies at
with the Multi-Unit Spectroscopic Explorer (MUSE) on the VLT. Making
use of the first 24 MUSE-Wide pointings in GOODS-South, each having an
integration time of 1 hour, we detect 100 Ly emitters and find
for most of the redshift range covered, with 29
per cent of the Ly sample exhibiting rest equivalent widths (rest-EWs)
15\AA. Adopting a range of rest-EW cuts (0 - 75\AA), we find no evidence
of a dependence of on either redshift or UV luminosity.Comment: 10 pages, 5 figures (MNRAS, updated as per version in press
Where Cosmic Dawn Breaks First: Mapping the Primordial Overdensity Powering a z 9 Ionized Bubble
Where Cosmic Dawn Breaks First: Mapping the Primordial Overdensity Powering a z 9 Ionized Bubble
Where Cosmic Dawn Breaks First: Mapping the Primordial Overdensity Powering a z 9 Ionized Bubble
Where Cosmic Dawn Breaks First: Mapping the Primordial Overdensity Powering a z 9 Ionized Bubble
Models of cosmic reionization predict that the earliest star-forming systems develop in primordial overdensities which, in turn, create ionized bubbles. With time, these bubbles grow and coalesce until the intergalactic medium is fully ionized. Since Lyman-alpha photons originating in these protoclusters can propagate freely through ionized gas, the highest redshift Lyman Alpha emitters (LAEs) act as valuable tracers of early ionized bubbles. We present evidence that the highest redshift LAE, EGSz8p7 (z=8.68), is likely embedded in such an overdensity. Collectively, in all of HST's deep fields, blank fields and gravitationally-lensed fields spanning >1000 arcmin^2 there are ~30 photometric candidates at z~9, yet a third lie within 3.75' (10 cMpc) of EGSz8p7. To confirm and exploit this extraordinary early overdensity we seek systemic redshifts and diagnostic features only JWST can provide. We propose blind, grism spectroscopy to map the ionized bubble around EGSz8p7 using the [OIII] doublet. A blind survey is optimal for determining a complete census of EGSz8p7's physical neighbors. Spitzer/IRAC color excesses at z>8 imply extreme [OIII] EWs (~6000 A) ensuring efficient use of JWST. Stellar population modeling of the sources around EGSz8p7 may give us the strongest constraints yet on when star-formation first commenced after the Big Bang (i.e., cosmic dawn). Our spectra will likewise constrain the ionizing photon production efficiency, a key unknown in reionization calculations. Our observing strategy is designed for maximum legacy value with a footprint overlapping the CEERS ERS survey and use of the wide F444W grism that will guarantee additional
The Synchrony of Production & Escape:Half the Bright Ly Emitters at have Lyman Continuum Escape Fractions
The ionizing photon escape fraction (LyC ) of star-forming galaxies is the single greatest unknown in the reionization budget. Stochastic sightline effects prohibit the direct separation of LyC leakers from non-leakers at significant redshift. Here we circumvent this uncertainty by inferring with resolved (R>4000) LyA profiles from the X-SHOOTER LyA survey at z=2 (XLS-z2). We select leakers (%) and non-leakers ( LyA emitters (LAEs). With median stacked spectra of these subsets covering 1000-8000 {\AA} (rest-frame) we investigate the conditions for LyC . We find the following differences between leakers vs. non-leakers: (i) strong nebular CIV and HeII emission vs. non-detections, (ii) O32~8.5 vs. ~3, (iii) Ha/Hb indicating no dust vs. E(B-V)~0.3, (iv) MgII emission close to the systemic velocity vs. redshifted, optically thick MgII, (v) LyA of ~50% vs. ~10%. The extreme EWs in leakers (O3+Hb~1100 {\AA}) constrain the characteristic timescale of LyC escape to ~3-10 Myr bursts when short-lived stars with the hardest ionizing spectra shine. The defining traits of leakers -- extremely ionizing stellar populations, low column densities, a dust-free, high ionization state ISM -- occur simultaneously in the stack, suggesting they are causally connected, and motivating why indicators like O32 may suffice to constrain at z>6 with JWST. The leakers comprise half our sample, have a median LyC ~50%, and an ionising production efficiency ~25.9. These results show LAEs -- the type of galaxies rare at z=2, but that become the norm at higher redshift -- are highly efficient ionizers, with extreme and prolific occurring in sync. (ABRIDGED
The synchrony of production and escape: half the bright Lyα emitters at z â 2 have Lyman continuum escape fractions â50 per cent
The ionizing photon escape fraction [Lyman continuum (LyC) fesc] of star-forming galaxies is the single greatest unknown in the reionization budget. Stochastic sightline effects prohibit the direct separation of LyC leakers from non-leakers at significant redshifts. Here we circumvent this uncertainty by inferring fesc using resolved (R > 4000) Lyman α (Lyα) profiles from the X-SHOOTER Lyα survey at z = 2 (XLS-z2). With empirically motivated criteria, we use Lyα profiles to select leakers () and non-leakers ({\approx} 50{{\ \rm per\ cent}}{\approx} 10{{\ \rm per\ cent}}\mathrm{ H}\beta \approx 1100f_{\rm esc} > 20{{\ \rm per\ cent}}f_{\rm esc} \approx 50{{\ \rm per\ cent}}20\!-\!55{{\ \rm per\ cent}}\log ({\xi _{\rm {ion}}/\rm {Hz\ erg^{-1}}})\approx 25.9$ (conservative range: 25.7-25.9). These results show LAEs - the type of galaxies rare at z â 2, but that become the norm at higher redshift - are highly efficient ionizers, with extreme Οion and prolific fesc occurring in sync
The MUSE-Wide Survey: A determination of the Lyman
We investigate the Lyman α emitter (LAE) luminosity function (LF) within the redshift range 2.9ââ€âzââ€â6 from the first instalment of the blind integral field spectroscopic MUSE-Wide survey. This initial part of the survey probes a region of 22.2 arcmin2 in the CANDELS/GOODS-S field (24 MUSE pointings with 1h integrations). The dataset provided us with 237 LAEs from which we construct the LAE LF in the luminosity range 42.2 †log LLyα[erg sâ1] †43.5 within a volume of 2.3â
Ăâ
105 Mpc3. For the LF construction we utilise three different non-parametric estimators: the classical 1/Vmax method, the Câ method, and an improved binned estimator for the differential LF. All three methods deliver consistent results, with the cumulative LAE LF being Ί(log L Lyα[erg sâ1] = 43.5) â 3 Ă 10â6 Mpcâ3 and Ί(log L Lyα[erg sâ1] = 42.2) â 2 Ă 10â3 Mpcâ3 towards the bright and faint end of our survey, respectively. By employing a non-parametric statistical test, and by comparing the full sample to subsamples in redshift bins, we find no supporting evidence for an evolving LAE LF over the probed redshift and luminosity range. Using a parametric maximum-likelihood technique we determine the best-fitting Schechter function parameters and with the corresponding normalisation logÏ*[Mpcâ3]=â
ââ
2.71. However, the dynamic range in Lyα luminosities probed by MUSE-Wide leads to a strong degeneracy between α and L*. Moreover, we find that a power-law parameterisation of the LF appears to be less consistent with the data compared to the Schechter function, even so when not excluding the X-Ray identified AGN from the sample. When correcting for completeness in the LAE LF determinations, we take into account that LAEs exhibit diffuse extended low surface brightness halos. We compare the resulting LF to one obtained by applying a correction assuming compact point-like emission. We find that the standard correction underestimates the LAE LF at the faint end of our survey by a factor of 2.5. Contrasting our results to the literature we find that at 42.2 †log LLyα[erg sâ1] âČ 42.5 previous LAE LF determinations from narrow-band surveys appear to be affected by a similar bias
The MUSE eXtremely Deep Field: Individual detections of Lyα haloes around rest-frame UV-selected galaxies at z â 2.9â4.4
International audienceHydrogen Lyα haloes (LAHs) are commonly used as a tracer of the circumgalactic medium (CGM) at high redshifts. In this work, we aim to explore the existence of Lyα haloes around individual UV-selected galaxies, rather than around Lyα emitters (LAEs), at high redshifts. Our sample was continuum-selected with F775Wââ€â27.5, and spectroscopic redshifts were assigned or constrained for all the sources thanks to the deepest (100- to 140-h) existing Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) data with adaptive optics. The final sample includes 21 galaxies that are purely F775W-magnitude selected within the redshift range zâââ2.9â
ââ
4.4 and within a UV magnitude range â20ââ€âM1500ââ€ââ18, thus avoiding any bias toward LAEs. We tested whether galaxyâs Lyα emission is significantly more extended than the MUSE PSF-convolved continuum component. We find 17 LAHs and four non-LAHs. We report the first individual detections of extended Lyα emission around non-LAEs. The Lyα halo fraction is thus as high as 81.0â11.2+10.3%, which is close to that for LAEs at zâ=â3â
ââ
6 in the literature. This implies that UV-selected galaxies generally have a large amount of hydrogen in their CGM. We derived the mean surface brightness (SB) profile for our LAHs with cosmic dimming corrections and find that Lyα emission extends to 5.4 arcsec (â40 physical kpc at the midpoint redshift zâ=â3.6) above the typical 1Ï SB limit. The incidence rate of surrounding gas detected in Lyα per one-dimensional line of sight per unit redshift, dn/dz, is estimated to be 0.76â0.09+0.09 for galaxies with M1500ââ€ââ18 mag at zâââ3.7. Assuming that Lyα emission and absorption arise in the same gas, this suggests, based on abundance matching, that LAHs trace the same gas as damped Lyα systems (DLAs) and sub-DLAs.Key words: galaxies: high-redshift / galaxies: formation / galaxies: evolution / galaxies: halos / cosmology: observationsâ Based on observations made with ESO telescope at the La Silla Paranal Observatory under the large program 1101.A-0127