ABSTRACT
We analyse the chemical properties of three z∼ 8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space ...Telescope. Exploiting O iiiλ4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12 + log(O/H)≈ 7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass–metallicity plane, the two galaxies at z ∼ 7.6 ($\rm log(M_*/M_{\odot }) = 8.1, 8.7$) have metallicities that are consistent with the extrapolation of the mass–metallicity relation at z∼2–3, while the least massive galaxy at z ∼ 8.5 ($\rm log(M_*/M_{\odot }) = 7.8$) shows instead a significantly lower metallicity. The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z∼ 7.6) being marginally consistent, while the z∼ 8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation, and metal enrichment in place at later epochs.
Abstract
We present a sample of four emission-line galaxies at
z
= 6.11–6.35 that were serendipitously discovered using the commissioning data for the James Webb Space Telescope (JWST)/NIRCam ...wide-field slitless spectroscopy mode. One of them (at
z
= 6.11) has been reported previously, while the others are new discoveries. These sources are selected by the secure detections of both O
iii
λ
5007 and H
α
lines with other fainter lines, which were tentatively detected in some cases (e.g., O
ii
λ
3727, O
iii
λ
4959). In the O
iii
/H
β
–N
ii
/H
α
Baldwin–Phillips–Terlevich diagram, these galaxies occupy the same parameter space as that of
z
∼ 2 star-forming galaxies, indicating that they have been enriched rapidly to subsolar metallicities (∼0.4
Z
⊙
), similar to galaxies with comparable stellar masses at much lower redshifts. The detection of strong H
α
lines suggests a higher ionizing photon production efficiency within galaxies in the early universe. We find brightening of the O
iii
λ
5007 line-luminosity function (LF) from
z
= 3 to 6, and weak or no redshift evolution of the H
α
line LF from
z
= 2 to 6. Both LFs are underpredicted at
z
∼ 6 by a factor of ∼10 in certain cosmological simulations. This further indicates a global Ly
α
photon escape fraction of 7%–10% at
z
∼ 6, which is slightly lower than previous estimates through the comparison of the UV-derived star formation rate density and Ly
α
luminosity density. Our sample recovers
66
−
44
+
128
% of
z
= 6.0–6.6 galaxies in the survey volume with stellar masses greater than 5 × 10
8
M
⊙
, suggesting the ubiquity of strong H
α
and O
iii
line emitters in the Epoch of Reionization, which will be further uncovered in the era of JWST.
In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that ...pass through or within 30degrees of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is approximately 11,000 deg super(2), or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be approximately 2.0 x 10 super(9) M sub(middot in circle) (d/55 kpc) super(2), with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar HI mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass.
Aim: The aim of this study was to evaluate the intracanal effectiveness of cryotherapy, curcumin irrigant, and normal saline as a final irrigant in reducing postendodontic pain in primary teeth. ...Materials and Methods: A total of 120 teeth between the ages of 4 and 7 years requiring pulpectomy in primary teeth were included in the study. The teeth were randomly assigned to one of the three treatment groups: intracanal cryotherapy using 2.5°C cold saline, curcumin irrigant, or normal saline. Following completion of chemomechanical preparation, final irrigation with 2.5°C cold saline, curcumin irrigant, and normal saline solution at room temperature were employed in the groups. Participants were asked to rate the severity of their postoperative pain on the Visual Analog Scale before, immediate postoperative after wearing of local anesthetic effect, and 24 h after the procedure. The results were analyzed statistically. Results: The differences in reduction of postendodontic pain between the three irrigating regimens were statistically not significant. Cryotherapy utilizing 2.5°C cold saline or curcumin irrigant can be used instead of normal saline as a final irrigant in pulpectomy of primary teeth. Conclusions: Cryotherapy can be a straightforward, cost-effective, and nontoxic treatment option for the management of postendodontic pain. Curcumin irrigant with its anti-inflammatory properties is also a better alternative as a final irrigant for reducing postoperative pain in primary teeth.
Abstract
The dramatic first images with JWST demonstrated its power to provide unprecedented spatial detail for galaxies in the high-redshift universe. Here, we leverage the resolution and depth of ...the JWST Cosmic Evolution Early Release Science Survey data in the Extended Groth Strip to perform pixel-level morphological classifications of galaxies in JWST F150W imaging using the Morpheus deep-learning framework for astronomical image analysis. By cross-referencing with existing photometric redshift catalogs from the Hubble Space Telescope (HST) CANDELS survey, we show that JWST images indicate the emergence of disk morphologies before
z
∼ 2 and with candidates appearing as early as
z
∼ 5. By modeling the light profile of each object and accounting for the JWST point-spread function, we find the high-redshift disk candidates have exponential surface brightness profiles with an average Sérsic index 〈
n
〉 = 1.04 and >90% displaying “disky” profiles (
n
< 2). Comparing with prior Morpheus classifications in CANDELS we find that a plurality of JWST disk galaxy candidates were previously classified as
compact
based on the shallower HST imagery, indicating that the improved optical quality and depth of the JWST helps to reveal disk morphologies that were hiding in the noise. We discuss the implications of these early disk candidates on theories for cosmological disk galaxy formation.
Abstract
Ly
α
line profiles are a powerful probe of interstellar medium (ISM) structure, outflow speed, and Lyman-continuum escape fraction. In this paper, we present the Ly
α
line profiles of the ...Cosmic Origins Spectrograph (COS) Legacy Archive Spectroscopic SurveY, a sample rich in spectroscopic analogs of reionization-era galaxies. A large fraction of the spectra show a complex profile, consisting of a double-peaked Ly
α
emission profile in the bottom of a damped, Ly
α
absorption trough. Such profiles reveal an inhomogeneous ISM. We successfully fit the damped Ly
α
absorption and the Ly
α
emission profiles separately, but with complementary covering factors, a surprising result because this approach requires no Ly
α
exchange between high-
N
H
i
and low-
N
H
i
paths. The combined distribution of column densities is qualitatively similar to the bimodal distributions observed in numerical simulations. We find an inverse relation between Ly
α
peak separation and the O
iii
/O
ii
flux ratio, confirming that the covering fraction of Lyman-continuum-thin sightlines increases as the Ly
α
peak separation decreases. We combine measurements of Ly
α
peak separation and Ly
α
red peak asymmetry in a diagnostic diagram, which identifies six Lyman-continuum leakers in the COS Legacy Archive Spectrocopy SurveY (CLASSY) sample. We find a strong correlation between the Ly
α
trough velocity and the outflow velocity measured from interstellar absorption lines. We argue that greater vignetting of the blueshifted Ly
α
peak, relative to the redshifted peak, is the source of the well-known discrepancy between shell-model parameters and directly measured outflow properties. The CLASSY sample illustrates how scattering of Ly
α
photons outside the spectroscopic aperture reshapes Ly
α
profiles because the distances to these compact starbursts span a large range.
Abstract In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch ...of reionization ( z > 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called “UV–BPT diagrams”—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (e.g., gas-phase metallicity, ionization parameter, carbon abundance, and stellar age). We find that the combination of C iii λ λ 1907,9 He ii λ 1640 and O iii λ 1666 can be a powerful tool to separate between SF, shocks, and AGN at subsolar metallicities. We also confirm that alternative diagrams without O iii λ 1666 still allow us to define an SF-locus, with some caveats. Diagrams including C iv λ λ 1548,51 should be taken with caution given the complexity of this doublet profile. Finally, we present a discussion detailing the ISM conditions required to detect UV emission lines, visible only in low gas-phase metallicity (12 + log(O/H) ≲ 8.3) and high ionization parameter (log( U ) ≳ −2.5) environments. Overall, CLASSY and our UV toolkit will be crucial in interpreting the spectra of the earliest galaxies that JWST is currently revealing.
Abstract
We present a first look at the MRS observations of the nucleus of the nearby galaxy M83, taken with MIRI on board JWST. The observations show a rich set of emission features from the ionized ...gas, warm molecular gas, and dust. To begin dissecting the complex processes in this part of the galaxy, we divide the observations into four different regions. We find that the strength of the emission features varies strongly from region to region, with the southeast region displaying the weakest features tracing the dust continuum and interstellar medium (ISM) properties. Comparison between the cold molecular gas traced by the
12
CO (1–0) transition with the Atacama Large Millimeter/submillimeter Array and the H
2
S(1) transition shows a similar spatial distribution. This is in contrast to the distribution of the much warmer H
2
emission from the S(7) transition found to be concentrated around the optical nucleus. We use the rotational emission lines and model the H
2
excitation to estimate a total molecular gas mass accounting for the warm H
2
component of
M
(>50 K)
H
2
= 67.90 (±5.43) × 10
6
M
⊙
. We compare this value to the total gas mass inferred by probing the cold H
2
gas through the
12
CO (1–0) emission,
M
(CO)
H
2
= 17.15 × 10
6
M
⊙
. We estimate that ∼75% of the total molecular gas mass is contained in the warm H
2
component. We also identify O
iv
25.89
μ
m and Fe
ii
25.99
μ
m emission. We propose that the diffuse Fe
ii
25.99
μ
m emission might be tracing shocks created during the interactions between the hot wind produced by the starburst and the much cooler ISM above the galactic plane. More detailed studies are needed to confirm such a scenario.
Abstract To study the chemical evolution across cosmic epochs, we investigate Ne, S, Cl, and Ar abundance patterns in the Cosmic Origins Spectrograph Legacy Archive Spectroscopic SurveY (CLASSY). ...CLASSY comprises local star-forming galaxies (SFGs; 0.02 < z < 0.18) with enhanced star formation rates, making them strong analogues to high- z SFGs. With direct measurements of electron temperature, we derive accurate ionic abundances for all elements and assess ionization correction factors (ICFs) to account for unseen ions and derive total abundances. We find Ne/O, S/O, Cl/O, and Ar/O exhibit constant trends with gas-phase metallicity for 12+log(O/H) < 8.5 but significant correlation for Ne/O and Ar/O with metallicity for 12+log(O/H) > 8.5, likely due to ICFs. Thus, the applicability of the ICFs to integrated spectra of galaxies could bias results, underestimating true abundance ratios. Using CLASSY as a local reference, we assess the evolution of Ne/O, S/O, and Ar/O in galaxies at z > 3, finding no cosmic evolution of Ne/O, while the lack of direct abundance determinations for S/O and Ar/O can bias the interpretation of the evolution of these elements. We determine the fundamental metallicity relationship (FMR) for CLASSY and compare to the high-redshift FMR, finding no evolution. Finally, we perform the first mass–neon relationship analysis across cosmic epochs, finding a slight evolution to high Ne at later epochs. The robust abundance patterns of CLASSY galaxies and their broad range of physical properties provide essential benchmarks for interpreting the chemical enrichment of the early galaxies observed with the JWST.
![First Sample of Hα+[O iii]λ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "First Sample of Hα+[O iii]λ5007 Line Emitters at z > 6 Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line-luminosity Functions")
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