We present the MOSFIRE spectroscopy of 13 candidate z ∼ 8 galaxies selected as Y-dropouts as part of the Brightest of Reionization Galaxies pure parallel survey. We detect no significant Lyα emission ...(our median 1σ rest-frame equivalent width sensitivity is in the range 2-16 Å). Using the Bayesian framework derived in a previous paper, we perform a rigorous analysis of a statistical subsample of non-detections for 10 Y-dropouts, including data from the literature, to study the cosmic evolution of the Lyα emission of Lyman break galaxies. We find that Lyα emission is suppressed at z ∼ 8 by at least a factor of three with respect to z ∼ 6 continuing the downward trend found by previous studies of z-dropouts at z ∼ 7. This finding suggests a dramatic evolution in the conditions of the intergalactic or circumgalactic media in just 300 Myr, consistent with the onset of reionization or changes in the physical conditions of the first generations of star-forming regions.
ABSTRACT We present the first study of the spatial distribution of star formation in z ∼ 0.5 cluster galaxies. The analysis is based on data taken with the Wide Field Camera 3 as part of the Grism ...Lens-Amplified Survey from Space (GLASS). We illustrate the methodology by focusing on two clusters (MACS 0717.5+3745 and MACS 1423.8+2404) with different morphologies (one relaxed and one merging) and use foreground and background galaxies as a field control sample. The cluster+field sample consists of 42 galaxies with stellar masses in the range 108-1011 M and star formation rates in the range 1-20 M yr−1. Both in clusters and in the field, H is more extended than the rest-frame UV continuum in 60% of the cases, consistent with diffuse star formation and inside-out growth. In ∼20% of the cases, the H emission appears more extended in cluster galaxies than in the field, pointing perhaps to ionized gas being stripped and/or star formation being enhanced at large radii. The peak of the H emission and that of the continuum are offset by less than 1 kpc. We investigate trends with the hot gas density as traced by the X-ray emission, and with the surface mass density as inferred from gravitational lens models, and find no conclusive results. The diversity of morphologies and sizes observed in H illustrates the complexity of the environmental processes that regulate star formation. Upcoming analysis of the full GLASS data set will increase our sample size by almost an order of magnitude, verifying and strengthening the inference from this initial data set.
The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. ...It has previously been shown that if the pseudo phase-space density, image, is a beautifully simple power law in radius, with the "golden values" image and image (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why image, and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.
We present the first measurements of the Lyman-continuum photon production efficiency ξion, 0 at z ∼ 4–5 for galaxies fainter than 0.2 L* (−19 mag). ξion, 0 quantifies the production rate of ionizing ...photons with respect to the UV luminosity density assuming a fiducial escape fraction of zero. Extending previous measurements of ξion, 0 to the faint population is important, as ultra-faint galaxies are expected to contribute the bulk of the ionizing emissivity. We probe ξion, 0 to such faint magnitudes by taking advantage of 200-h depth Spitzer/IRAC observations from the GREATS program and ≈300 3 < z < 6 galaxies with spectroscopic redshifts from the MUSE GTO Deep + Wide programs. Stacked IRAC 3.6−4.5 colors are derived and used to infer the Hα rest-frame equivalent widths, which range from 403 Å to 2818 Å. The derived ξion, 0 is log10(ξion,0/Hz erg−1) = 25.36 ± 0.08 over −20.5 < MUV < −17.5, similar to those derived for brighter galaxy samples at the same redshift and therefore suggesting that ξion shows no strong dependence on MUV. The ξion, 0 values found in our sample imply that the Lyman-continuum escape fraction for MUV ≈ −19 star-forming galaxies cannot exceed ≈8–20% in the reionization era.
Abstract
We present the results of ALMA spectroscopic follow-up of a
z
= 6.766 Ly
α
emitting galaxy behind the cluster RX J1347.1−1145. We report the detection of C
ii
158
μ
m line fully consistent ...with the Ly
α
redshift and with the peak of the optical emission. Given the magnification of
μ
= 5.0 ± 0.3, the intrinsic (corrected for lensing) luminosity of the C
ii
line is
L
C
ii
, roughly ∼5 times fainter than other detections of
z
∼ 7 galaxies. The result indicates that low
L
C
ii
in
z
∼ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset (
) between the Ly
α
and C
ii
line is unusual, and may be indicative of ionizing photons escaping.
The MUSE Hubble Ultra Deep Field Survey Maseda, Michael V.; Brinchmann, Jarle; Franx, Marijn ...
Astronomy and astrophysics (Berlin),
12/2017, Letnik:
608
Journal Article
Recenzirano
Odprti dostop
The C III
λλ
1907, 1909 emission doublet has been proposed as an alternative to Lyman-
α
in redshift confirmations of galaxies at
z
≳ 6 since it is not attenuated by the largely neutral intergalactic ...medium at these redshifts and is believed to be strong in the young, vigorously star-forming galaxies present at these early cosmic times. We present a statistical sample of 17 C III-emitting galaxies beyond
z
~ 1.5 using ~30 h deep VLT/MUSE integral field spectroscopy covering 2 square arcminutes in the
Hubble
Deep Field South (HDFS) and Ultra Deep Field (UDF), achieving C III sensitivities of ~ 2 × 10
-17
erg s
-1
cm
-2
in the HDFS and ~ 7 × 10
-18
erg s
-1
cm
-2
in the UDF. The rest-frame equivalent widths range from 2 to 19 Å. These 17 galaxies represent ~3% of the total sample of galaxies found between 1.5 ≲
z
≲ 4. They also show elevated star formation rates, lower dust attenuation, and younger mass-weighted ages than the general population of galaxies at the same redshifts. Combined with deep slitless grism spectroscopy from the HST/WFC3 in the UDF, we can tie the rest-frame ultraviolet C III emission to rest-frame optical emission lines, namely O III
λ
5007, finding a strong correlation between the two. Down to the flux limits that we observe (~ 1 × 10
-18
erg s
-1
cm
-2
with the grism data in the UDF), all objects with a rest-frame O III
λλ
4959, 5007 equivalent width in excess of 250 Å, the so-called extreme emission line galaxies, have detections of C III in our MUSE data. More detailed studies of the C III-emitting population at these intermediate redshifts will be crucial to understand the physical conditions in galaxies at early cosmic times and to determine the utility of C III as a redshift tracer.
The MUSE Hubble Ultra Deep Field Survey Feltre, Anna; Maseda, Michael V.; Bacon, Roland ...
Astronomy and astrophysics (Berlin),
09/2020, Letnik:
641
Journal Article
Recenzirano
Odprti dostop
We investigated the ultraviolet (UV) spectral properties of faint Lyman-
α
emitters (LAEs) in the redshift range 2.9 ≤
z
≤ 4.6, and we provide material to prepare future observations of the faint ...Universe. We used data from the MUSE
Hubble
Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median
M
UV
of −18 and down to
M
UV
of −16), low stellar mass (median value of 10
8.4
M
⊙
and down to 10
7
M
⊙
) LAEs at redshift
z
≳ 3. We computed various averaged spectra of LAEs, subsampled on the basis of their observational (e.g., Ly
α
strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and star-formation rate) properties. We searched for UV spectral features other than Ly
α
, such as higher ionization nebular emission lines and absorption features. We successfully observed the O
III
λ
1666 and C
III
λ
1907+C
III
λ
1909 collisionally excited emission lines and the He
II
λ
1640 recombination feature, as well as the resonant C
IV
λ
λ
1548,1551 doublet either in emission or P-Cygni. We compared the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Ly
α
equivalent widths, fainter UV magnitudes, bluer UV spectral slopes, and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of
z
> 2 galaxies. This suggests that weak UV features are likely ubiquitous in high
z
, low-mass, and faint LAEs. We publicly released the stacked spectra, as they can serve as empirical templates for the design of future observations, such as those with the
James Webb
Space Telescope and the Extremely Large Telescope.
ABSTRACT We conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. We use a ...Bayesian quasar selection algorithm to identify 35,820 type 1 quasar candidates in a 239 field of the Sloan Digital Sky Survey (SDSS) Stripe 82, using a combination of optical photometry and variability. Color analysis is performed on 5-band single- and multi-epoch SDSS optical photometry to a depth of From these data, variability parameters are calculated by fitting the structure function of each object in each band with a power-law model using 10 to observations over timescales from ∼1 day to ∼8 years. Selection was based on a training sample of 13,221 spectroscopically confirmed type-1 quasars, largely from the SDSS. Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency, respectively, with particular improvement in the selection of quasars at where quasars and stars have similar optical colors. The 22,867 quasar candidates that are not spectroscopically confirmed reach a depth of 21,876 (95.7%) are dimmer than coadded i-band magnitude of 19.9, the cutoff for spectroscopic follow-up for SDSS on Stripe 82. Brighter than 19.9, we find 5.7% more quasar candidates without confirming spectra in sky regions otherwise considered complete. The resulting quasar sample has sufficient purity (and statistically correctable incompleteness) to produce a luminosity function comparable to those determined by spectroscopic investigations. We discuss improvements that can be made to the process in preparation for performing similar photometric selection and science on data from post-SDSS sky surveys.
A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are ...expected to be overabundant in globular clusters compared with in the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extracted the spectrum of the nebula and used the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios were used to determine the electron temperature and density. It is estimated to have a mass of 1–17 × 10−5M⊙. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a “guest star”, an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extra-solar events recorded in human history.
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![ALMA [C ii] 158 μm Detectio...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2041-8205_2041-8213/small "ALMA [C ii] 158 μm Detection of a Redshift 7 Lensed Galaxy behind RX J1347.1−1145")
