Largescale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ringlike structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ∼0.″3 (30 pc) resolution new JWST/MIRI imaging with archival ALMA CO(2–1) mapping of the central ∼5 kpc of the nearby barred spiral galaxy NGC 1365 to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two wellknown bright bar lanes that surround a smooth dynamically cold gas disk (
We present maps tracing the fraction of dust in the form of polycyclic aromatic hydrocarbons (PAHs) in IC 5332, NGC 628, NGC 1365, and NGC 7496 from JWST/MIRI observations. We trace the PAH fraction by combining the F770W (7.7
 NSFPAR ID:
 10397381
 Author(s) / Creator(s):
 ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
 Publisher / Repository:
 DOI PREFIX: 10.3847
 Date Published:
 Journal Name:
 The Astrophysical Journal Letters
 Volume:
 944
 Issue:
 2
 ISSN:
 20418205
 Format(s):
 Medium: X Size: Article No. L11
 Size(s):
 ["Article No. L11"]
 Sponsoring Org:
 National Science Foundation
More Like this

Abstract R _{gal}∼ 475 pc) reminiscent of nonstarforming disks in earlytype galaxies and likely fed by gas inflow triggered by stellar feedback in the lanes. The lanes host a large number of JWSTidentified massive young star clusters. We find some evidence for temporal star formation evolution along the ring. The complex kinematics in the gas lanes reveal strong streaming motions and may be consistent with convergence of gas streamlines expected there. Indeed, the extreme line widths are found to be the result of inter“cloud” motion between gas peaks;ScousePy decomposition reveals multiple components with line widths of 〈σ _{CO,scouse}〉 ≈ 19 km s^{−1}and surface densities of , similar to the properties observed throughout the rest of the central molecular gas structure. Tailored hydrodynamical simulations exhibit many of the observed properties and imply that the observed structures are transient and highly timevariable. From our study of NGC 1365, we conclude that it is predominantly the high gas inflow triggered by the bar that is setting the star formation in its CMZ. $\u3008\phantom{\rule{0.25em}{0ex}}{\mathrm{\Sigma}}_{{\mathrm{H}}_{2},\mathrm{scouse}}\u3009\phantom{\rule{0.25em}{0ex}}\approx \phantom{\rule{0.25em}{0ex}}800\phantom{\rule{0.25em}{0ex}}{M}_{\odot}\phantom{\rule{0.25em}{0ex}}{\mathrm{pc}}^{2}$ 
Abstract We present a Keck/MOSFIRE restoptical composite spectrum of 16 typical gravitationally lensed starforming dwarf galaxies at 1.7 ≲
z ≲ 2.6 (z _{mean}= 2.30), all chosen independent of emissionline strength. These galaxies have a median stellar mass of and a median star formation rate of $\mathrm{log}{({M}_{*}/{M}_{\odot})}_{\mathrm{med}}={8.29}_{0.43}^{+0.51}$ . We measure the faint electrontemperaturesensitive [O ${\mathrm{S}\mathrm{F}\mathrm{R}}_{\mathrm{H}\alpha}^{\mathrm{m}\mathrm{e}\mathrm{d}}={2.25}_{1.26}^{+2.15}\phantom{\rule{0.25em}{0ex}}{M}_{\odot}\phantom{\rule{0.25em}{0ex}}{\mathrm{y}\mathrm{r}}^{1}$iii ]λ 4363 emission line at 2.5σ (4.1σ ) significance when considering a bootstrapped (statisticalonly) uncertainty spectrum. This yields a directmethod oxygen abundance of ( $12+\mathrm{log}{(\mathrm{O}/\mathrm{H})}_{\mathrm{direct}}={7.88}_{0.22}^{+0.25}$ ). We investigate the applicability at high ${0.15}_{0.06}^{+0.12}\phantom{\rule{0.33em}{0ex}}{Z}_{\odot}$z of locally calibrated oxygenbased strongline metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strongline ratio. At fixedM _{*}, our composite is well represented by thez ∼ 2.3 directmethod stellar mass—gasphase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed $(\mathrm{log}{({M}_{*}/{M}_{\odot})}_{\mathrm{med}}={8.92}_{0.22}^{+0.31})$M _{*}and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [Oii ]λ 3729/[Oii ]λ 3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of ( ${n}_{e}={1}_{0}^{+215}\phantom{\rule{0.33em}{0ex}}{\mathrm{cm}}^{3}$ ) when considering the bootstrapped (statisticalonly) error spectrum. This result suggests that lowermass galaxies have lower densities than highermass galaxies at ${n}_{e}={1}_{0}^{+74}\phantom{\rule{0.33em}{0ex}}{\mathrm{cm}}^{3}$z ∼ 2. 
Abstract Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at
z > 7 and largely ionized byz ∼ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volumeaveraged neutral fraction of the IGM is either relatively low ( ) or close to unity ( ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\lesssim {10}^{3}$ ). In particular, the neutral fraction evolution of the IGM at the critical redshift range of ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\sim 1$z = 6–7 is poorly constrained. We present new constraints on at ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}$z ∼ 5.1–6.8 by analyzing deep optical spectra of 53 quasars at 5.73 <z < 7.09. We derive modelindependent upper limits on the neutral hydrogen fraction based on the fraction of “dark” pixels identified in the Lyα and Lyβ forests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first modelindependent constraints on the IGM neutral hydrogen fraction atz ∼ 6.2–6.8 using quasar absorption measurements. Our results give upper limits of (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.3)<0.79\pm 0.04$σ ), (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.5)<0.87\pm 0.03$σ ), and (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.7)<{0.94}_{0.09}^{+0.06}$σ ). The dark pixel fractions atz > 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018. 
Abstract We present the
z ≈ 6 type1 quasar luminosity function (QLF), based on the PanSTARRS1 (PS1) quasar survey. The PS1 sample includes 125 quasars atz ≈ 5.7–6.2, with −28 ≲M _{1450}≲ −25. With the addition of 48 fainter quasars from the SHELLQs survey, we evaluate thez ≈ 6 QLF over −28 ≲M _{1450}≲ −22. Adopting a double power law with an exponential evolution of the quasar density (Φ(z ) ∝ 10^{k(z−6)};k = −0.7), we use a maximum likelihood method to model our data. We find a break magnitude of , a faintend slope of ${M}^{*}={26.38}_{0.60}^{+0.79}\phantom{\rule{0.25em}{0ex}}\mathrm{mag}$ , and a steep brightend slope of $\alpha ={1.70}_{0.19}^{+0.29}$ . Based on our new QLF model, we determine the quasar comoving spatial density at $\beta ={3.84}_{1.21}^{+0.63}$z ≈ 6 to be . In comparison with the literature, we find the quasar density to evolve with a constant value of $n({M}_{1450}<26)={1.16}_{0.12}^{+0.13}\phantom{\rule{0.25em}{0ex}}{\mathrm{cGpc}}^{3}$k ≈ −0.7, fromz ≈ 7 toz ≈ 4. Additionally, we derive an ionizing emissivity of , based on the QLF measurement. Given standard assumptions, and the recent measurement of the mean free path by Becker et al. at ${\u03f5}_{912}(z=6)={7.23}_{1.02}^{+1.65}\times {10}^{22}\phantom{\rule{0.25em}{0ex}}\mathrm{erg}\phantom{\rule{0.25em}{0ex}}{\mathrm{s}}^{1}\phantom{\rule{0.25em}{0ex}}{\mathrm{Hz}}^{1}\phantom{\rule{0.25em}{0ex}}{\mathrm{cMpc}}^{3}$z ≈ 6, we calculate an Hi photoionizing rate of Γ_{H I}(z = 6) ≈ 6 × 10^{−16}s^{−1}, strongly disfavoring a dominant role of quasars in hydrogen reionization. 
Abstract We analyze the COtoH_{2}conversion factor (
α _{CO}) in the nearby barred spiral galaxy M83. We present new Hi observations from the VLA and singledish GBT in the disk of the galaxy, and combine them with maps of CO(10) integrated intensity and dust surface density from the literature.α _{CO}and the gastodust ratio (δ _{GDR}) are simultaneously derived in annuli of 2 kpc width fromR = 1–7 kpc. We find thatα _{CO}andδ _{GDR}both increase radially, by a factor of ∼2–3 from the center to the outskirts of the disk. The luminosityweighted averages over the disk areα _{CO}= 3.14 (2.06, 4.96) and ${M}_{\odot}\phantom{\rule{0.25em}{0ex}}\phantom{\rule{0.25em}{0ex}}{\mathrm{pc}}^{2}{[\mathrm{K}\phantom{\rule{0.25em}{0ex}}\phantom{\rule{0.25em}{0ex}}\mathrm{km}\phantom{\rule{0.25em}{0ex}}{\mathrm{s}}^{1}]}^{1}$δ _{GDR}= 137 (111, 182) at the 68% (1σ ) confidence level. These are consistent with theα _{CO}andδ _{GDR}values measured in the Milky Way. In addition to possible variations ofα _{CO}due to the radial metallicity gradient, we test the possibility of variations inα _{CO}due to changes in the underlying cloud populations, as a function of galactic radius. Using a truncated powerlaw molecular cloud CO luminosity function and an empirical powerlaw relation for cloud mass and luminosity, we show that the changes in the underlying cloud population may account for a factor of ∼1.5–2.0 radial change inα _{CO}.