Abstract
Extreme emission-line galaxies (EELGs) at redshift
z
= 1−2 provide a unique view of metal-poor, starburst sources that are the likely drivers of the cosmic reionization at
z
≥ 6. However, ...the molecular gas reservoirs of EELGs—the fuel for their intense star formation—remain beyond the reach of current facilities. We present ALMA C
ii
and PdBI CO(2–1) observations of the
z
= 1.8, strongly lensed EELG SL2S 0217, a bright Ly
α
emitter with a metallicity 0.05
Z
⊙
. We obtain a tentative (∼3
σ
–4
σ
) detection of the C
ii
line and set an upper limit on the C
ii
/SFR (star-forming rate) ratio of ≤1 × 10
6
L
⊙
/(
M
⊙
yr
−1
), based on the synthesized images and visibility-plane analysis. The CO(2–1) emission is not detected. Photoionization modeling indicates that up to 80% of the C
ii
emission originates from neutral or molecular gas, although we cannot rule out that the gas is fully ionized. The very faint C
ii
emission is in line with both nearby metal-poor dwarfs and high-redshift Ly
α
emitters, and predictions from hydrodynamical simulations. However, the C
ii
line is 30× fainter than predicted by the De Looze et al. C
ii
–SFR relation for local dwarfs, illustrating the danger of extrapolating locally calibrated relations to high-redshift, metal-poor galaxies.
The amount of integral field spectrograph (IFS) data has grown considerably over the last few decades. The demand for tools to analyze such data is therefore bigger now than ever. We present a ...flexible Python tool for Three-Dimensional Optimal Spectral Extraction (TDOSE) from IFS data cubes. TDOSE works on any three-dimensional data cube and bases the spectral extractions on morphological reference image models. By default, these models are generated and composed of multiple multivariate Gaussian components, but can also be constructed with independent modeling tools and be provided as input to TDOSE. In each wavelength layer of the IFS data cube, TDOSE simultaneously optimizes all sources in the morphological model to minimize the difference between the scaled model components and the IFS data. The flux optimization produces individual data cubes containing the scaled three-dimensional source models. This allows the efficient de-blending of flux in both the spatial and spectral dimensions of the IFS data cubes, and extraction of the corresponding one-dimensional spectra. TDOSE implicitly requires an assumption about the two-dimensional light distribution. We describe how the flexibility of TDOSE can be used to mitigate and correct for deviations from the input distribution. Furthermore, we present an example of how the three-dimensional source models generated by TDOSE can be used to improve two-dimensional maps of physical parameters like velocity, metallicity, or star formation rate when flux contamination is a problem. By extracting TDOSE spectra of ∼150 OII emitters from the MUSE-Wide survey we show that the median increase in line flux is ∼5% when using multi-component models as opposed to single-component models. However, the increase in recovered line emission in individual cases can be as much as 50%. Comparing the TDOSE model-based extractions of the MUSE-Wide OII emitters with aperture spectra, the TDOSE spectra provides a median flux (S/N) increase of 9% (14%). Hence, TDOSE spectra optimize the S/N while still being able to recover the total emitted flux.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the ...lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-α transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 10
kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-α emission has been a long-standing goal of observational astrophysics
, but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-α emission from hydrogen around high-redshift galaxies
. Such measurements were previously limited to especially favourable systems
or to the use of massive statistical averaging
because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-α emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars
. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.
Full text
Available for:
KISLJ, NUK, SBMB, UL, UM, UPUK
ABSTRACT We present the first results and design from the redshift z ∼ 9-10 Brightest of the Reionizing Galaxies Hubble Space Telescope survey BoRGz9-10, aimed at searching for intrinsically luminous ...unlensed galaxies during the first 700 Myr after the Big Bang. BoRGz9-10 is the continuation of a multi-year pure-parallel near-IR and optical imaging campaign with the Wide Field Camera 3. The ongoing survey uses five filters, optimized for detecting the most distant objects and offering continuous wavelength coverage from λ = 0.35 m to λ = 1.7 m. We analyze the initial ∼130 arcmin2 of area over 28 independent lines of sight (∼25% of the total planned) to search for galaxies using a combination of Lyman-break and photometric redshift selections. From an effective comoving volume of (5-25) × 105 Mpc3 for magnitudes brighter than in the -band respectively, we find five galaxy candidates at 8.3-10 detected at high confidence ( ), including a source at 8.4 with ( ), which, if confirmed, would be the brightest galaxy identified at such early times ( ). In addition, BoRGz9-10 data yield four galaxies with . These new Lyman-break galaxies with are ideal targets for follow-up observations from ground and space-based observatories to help investigate the complex interplay between dark matter growth, galaxy assembly, and reionization.
We present a census of Lya emission at $z\gtrsim 7$, utilizing deep near-infrared Hubble Space Telescope grism spectroscopy from the first six completed clusters of the Grism Lens-Amplified Survey ...from Space (GLASS). In 24/159 photometrically selected galaxies we detect emission lines consistent with Lya in the GLASS spectra. Based on the distribution of signal-to-noise ratios and on simulations, we expect the completeness and the purity of the sample to be 40%-100% and 60%-90%, respectively. For the objects without detected emission lines we show that the observed 1s flux limits reach 5 x 10-18 erg s-1 cm-2 per position angle over the full wavelength range of GLASS. Based on the conditional probability of Lya emission measured from the ground at $z\sim 7$, we would have expected 12-18 Lya emitters. The candidates include a promising source at z = 8.1.
Abstract
We constrain the distribution of spatially offset Lyman-alpha emission (Ly α) relative to rest-frame ultraviolet emission in ∼300 high redshift (3 < z < 5.5) Lyman-break galaxies (LBGs) ...exhibiting Ly α emission from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep Survey and Chandra Deep Field South fields (≃0.2 deg2 total). Because slit spectroscopy only provides one spatial dimension, we use Bayesian inference to recover the underlying two-dimensional Ly α spatial offset distribution. We model the distribution using a two-dimensional circular Gaussian, defined by a single parameter σr,Ly α, the standard deviation expressed in polar coordinates. Over the entire redshift range of our sample (3 < z < 5.5), we find $\sigma _{r,\mathrm{Ly}\,\alpha }=1.70^{+0.09}_{-0.08}$ kpc ($68\hbox{ per cent}$ conf.), corresponding to ∼0${^{\prime\prime}_{.}}$25 at 〈z〉 = 4.5. We also find that σr,Ly α decreases significantly with redshift. Because Ly α spatial offsets can cause slit losses, the decrease in σr,Ly α with redshift can partially explain the increase in the fraction of Ly α emitters observed in the literature over this same interval, although uncertainties are still too large to reach a strong conclusion. If σr,Ly α continues to decrease into the reionization epoch, then the decrease in Ly α transmission from galaxies observed during this epoch might require an even higher neutral hydrogen fraction than what is currently inferred. Conversely, if spatial offsets increase with the increasing opacity of the intergalactic medium, slit losses may explain some of the drop in Ly α transmission observed at z > 6. Spatially resolved observations of Ly α and UV continuum at 6 < z < 8 are needed to settle the issue.
Abstract
The C
iii
and C
iv
rest-frame UV emission lines are powerful probes of the ionization states of galaxies. They have furthermore been suggested as alternatives for spectroscopic redshift ...confirmation of objects at the epoch of reionization (
), where the most frequently used redshift indicator, Ly
α
, is attenuated by the high fraction of neutral hydrogen in the intergalactic medium. However, currently only very few confirmations of carbon UV lines at these high redshifts exist, making it challenging to quantify these claims. Here, we present the detection of C
iv
λλ
1548, 1551 Å in
Hubble Space Telescope
slitless grism spectroscopy obtained by GLASS of a Ly
α
emitter at
z
= 6.11 multiply imaged by the massive foreground galaxy cluster RXC J2248.7–4431. The C
iv
emission is detected at the 3
σ
–5
σ
level in two images of the source, with marginal detection in two other images. We do not detect significant C
iii
λλ
1907, 1909 Å emission implying an equivalent width
Å (1
σ
) and
(2
σ
). Combined with limits on the rest-frame UV flux from the He
ii
λ
1640 Å emission line and the O
iii
λλ
1661, 1666 Å doublet, we put constraints on the metallicity and the ionization state of the galaxy. The estimated line ratios and equivalent widths do not support a scenario where an AGN is responsible for ionizing the carbon atoms. SED fits, including nebular emission lines, imply a source with a mass of log(
M
/
M
⊙
) ∼ 9, SFR of around 10
M
⊙
yr
−1
, and a young stellar population
old. The source shows a stronger ionizing radiation field than objects with detected C
iv
emission at
and adds to the growing sample of low-mass (log(
M
/
M
⊙
) ≲ 9) galaxies at the epoch of reionization with strong radiation fields from star formation.
Detections of Lyman-break galaxies (LBGs) at high-redshift are affected by gravitational lensing induced by foreground deflectors not only in galaxy clusters, but also in blank fields. We quantify ...the impact of strong magnification in the samples of B
435, V
606, i
775 and z
850 & Y
105 dropouts (4 ≲ z ≲ 8) observed in the eXtreme Deep Field (XDF) and the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) fields by investigating the proximity of dropouts to foreground objects. We find that ∼6 per cent of bright z ∼ 7 LBGs (
$m_{H_{160}}<26$
) have been strongly lensed (μ > 2) by foreground objects. This fraction decreases from ∼3.5 per cent at z ∼ 6 to ∼1.5 per cent at z ∼ 4. Since the observed fraction of strongly lensed LBGs is a function of the shape of the luminosity function (LF), it can be used to derive Schechter parameters, α and M
⋆, independently from galaxy number counts. Our magnification bias analysis yields Schechter-function parameters in close agreement with those determined from galaxy counts albeit with larger uncertainties. Extrapolation of our analysis to z ≳ 8 suggests that surveys with JWST, WFIRST and Euclid should find excess LBGs at the bright end, over an intrinsic exponential cutoff. Finally, we highlight how the magnification bias measurement near the XDF detection limit can be used to probe the population of galaxies beyond this limit. Preliminary results suggest that the magnification bias at M
UV ∼ −18 is weaker than expected if α ≲ −1.7 extends well below the current detection limits. This could imply a flattening of the LF at M
UV ≳ −16.5. However, selection effects and completeness estimates are difficult to quantify precisely. Thus, we do not rule out a steep LF extending to M
UV ≳ −15.
![Ultrafaint [C ii] Emission ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "Ultrafaint [C ii] Emission in a Redshift = 2 Gravitationally Lensed Metal-poor Dwarf Galaxy")
PDF
