札本 佳伸

In this work we study the efficiency of galactic feedback in the early Universe by stacking the [C II] 158um emission in a large sample of normal star-forming galaxies at 4 < z < 6, drawn from the ALMA Large Program to INvestigate [C II] at Early times (ALPINE) survey. Searching for typical signatures of outflows in the high-velocity tails of the stacked [C II] profile, we observe (i) deviations from a single-component Gaussian model in the combined residuals and (ii) broad emission in the stacked [C II] spectrum, at velocities of |v|<~ 500 km/s. Interestingly, the significance of these features increases when stacking the sub-group of galaxies with star formation rates (SFRs) higher than the median (SFRmed = 25 Msun/yr), confirming their star formation-driven nature. The estimated typical mass outflow rates are comparable with the SFRs, yielding mass-loading factors of the order of unity (similarly to local normal star-forming galaxies), thus suggesting that star formation-driven feedback does not play a dominant role in quenching galaxies at z > 4. From the stacking analysis of the datacubes, we find that the combined [C II] core emission (|v|< 200 km/s) of the higher SFR galaxies extends on physical sizes of ~30 kpc (diameter scale), well beyond the analogous [C II] core emission of lower SFR galaxies and the stacked FIR-continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochs....

We combine high-resolution ALMA and HST/CANDELS observations of 20 submillimeter galaxies (SMGs), predominantly from the AS2UDS survey at z ≃ 2, with bright rest-frame optical counterparts ({K}_{{ { s} } }≲ 22.9) to investigate the resolved structural properties of their dust and stellar components. We derive two-dimensional stellar-mass distributions that are inferred from spatial mass-to-light ratio ({\text{ } }M/{L}^* ) corrections based on rest-frame optical colors. Due to the high central column densities of dust in our SMGs, our mass distributions likely represent a lower limit to the true central mass density. The centroid positions between the inferred stellar-mass and the dust distributions agree within 1.1 kpc, indicating an overall good spatial agreement between the two components. The majority of our sources exhibit compact dust configurations relative to the stellar component (with a median ratio of effective radii {R}_{{ { e}},{dust } }/{R}_{{ { e}},* } = 0.6). This ratio does not change with specific star formation rate over the factor of 30 spanned by our targets, sampling the locus of “normal” main-sequence galaxies up to the starburst regime, {log}({sSFR}/{sSFR } }_MS})≥slant 0.5. Unlike typical spiral galaxies in the local universe, our results imply that massive SMGs are experiencing centrally enhanced star formation. The sizes and stellar densities of our SMGs are in agreement with those of the passive population at z = 1.5, which is consistent with these systems being the descendants of z ≃ 2 SMGs....

Disk galaxies at intermediate redshift (z 0.7) have been found in previous work to display more optically thick behaviour than their local counterparts in the rest-frame B-band surface brightness, suggesting an evolution in dust properties over the past 6 Gyr. We compare the measured luminosities of face-on and edge-on star-forming galaxies at different wavelengths (Ultraviolet (UV), mid-infrared (MIR), far-infrared (FIR), and radio) for two well-matched samples of disk-dominated galaxies: a local Sloan Digital Sky Survey (SDSS)-selected sample at z 0.07 and a sample of disks at z 0.7 drawn from Cosmic Evolution Survey (COSMOS). We have derived correction factors to account for the inclination dependence of the parameters used for sample selection. We find that typical galaxies are transparent at MIR wavelengths at both redshifts, and that the FIR and radio emission is also transparent as expected. However, reduced sensitivity at these wavelengths limits our analysis; we cannot rule out opacity in the FIR or radio. Ultra-violet attenuation has increased between z 0 and z 0.7, with the z 0.7 sample being a factor of 3.4 more attenuated. The larger UV attenuation at z 0.7 can be explained by more clumpy dust around nascent star-forming regions. There is good agreement between the fitted evolution of the normalisation of the SFR_UV versus 1 - cos(i) trend (interpreted as the clumpiness fraction) and the molecular gas fraction/dust fraction evolution of galaxies found out to z &lt; 1....

We present 1.3- and/or 3-mm continuum images and 3-mm spectral scans, obtained using Northern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter Array (ALMA), of 21 distant, dusty, star-forming galaxies. Our sample is a subset of the galaxies selected by Ivison et al. on the basis of their extremely red far-infrared (far-IR) colours and low Herschel flux densities; most are thus expected to be unlensed, extraordinarily luminous starbursts at z ≳ 4, modulo the considerable cross-section to gravitational lensing implied by their redshift. We observed 17 of these galaxies with NOEMA and four with ALMA, scanning through the 3-mm atmospheric window. We have obtained secure redshifts for seven galaxies via detection of multiple CO lines, one of them a lensed system at z = 6.027 (two others are also found to be lensed); a single emission line was detected in another four galaxies, one of which has been shown elsewhere to lie at z = 4.002. Where we find no spectroscopic redshifts, the galaxies are generally less luminous by 0.3-0.4 dex, which goes some way to explaining our failure to detect line emission. We show that this sample contains the most luminous known star-forming galaxies. Due to their extreme star-formation activity, these galaxies will consume their molecular gas in ≲ 100 Myr, despite their high molecular gas masses, and are therefore plausible progenitors of the massive, 'red-and-dead' elliptical galaxies at z ≈ 3....

We present results on the dust attenuation of galaxies at redshift ∼3-6 by studying the relationship between the UV spectral slope (β_UV) and the infrared excess (IRX; L_IR/L_UV) using Atacama Large Millimeter/submillimeter Array (ALMA) far-infrared continuum observations. Our study is based on a sample of 67 massive, star-forming galaxies with a median mass of M_* ∼ 10^10.7 M_☉ spanning a redshift range z = 2.6-3.7 (median z = 3.2) that were observed with ALMA at λ _{rest}=300 {μ m}. Both the individual ALMA detections (41 sources) and stacks including all galaxies show the IRX-β_UV relationship at z ∼ 3 is mostly consistent with that of local starburst galaxies on average. However, we find evidence for a large dispersion around the mean relationship by up to ±0.5 dex. Nevertheless, the locally calibrated dust correction factors based on the IRX-β_UV relation are on average applicable to main-sequence z ∼ 3 galaxies. This does not appear to be the case at even higher redshifts, however. Using public ALMA observations of z ∼ 4-6 galaxies we find evidence for a significant evolution in the IRX-β_UV and the IRX-M_* relations beyond z ∼ 3 towards lower IRX values. We discuss several caveats that could affect these results, including the assumed dust temperature. ALMA observations of larger z &gt; 3 galaxy sample spanning a wide range of physical parameters (e.g. lower stellar mass) will be important to investigate this intriguing redshift evolution further....

We detect 20 z = 7.0 Lyα emitter (LAE) candidates to L(Lyα) ̃ 2 × 10⁴² erg s^-1 or 0.3 {L}_z=7^* and in a volume of 6.1 × 10⁵ Mpc³ in the Subaru Deep Field and the Subaru/XMM-Newton Deep Survey field by 82 hr and 37 hr of Subaru Suprime-Cam narrowband NB973 and reddest optical y-band imaging. We compare their Lyα and UV luminosity functions (LFs) and densities and Lyα equivalent widths (EWs) to those of z = 5.7, 6.6, and 7.3 LAEs from previous Suprime-Cam surveys. The Lyα LF (density) rapidly declines by a factor of ×1.5 (1.9) in L(Lyα) at z = 5.7-6.6 (160 Myr), ×1.5 (1.6) at z = 6.6-7.0 (60 Myr) at the faint end, and ×2.0 (3.8) at z = 7.0-7.3 (40 Myr). Also, in addition to the systematic decrease in EW at z = 5.7-6.6 previously found, two-thirds of the z = 7.0 LAEs detected in the UV continuum exhibit lower EWs than the z = 6.6 ones. Moreover, while the UV LF and density do not evolve at z = 5.7-6.6, they modestly decline at z = 6.6-7.0, implying galaxy evolution contributing to the decline of the Lyα LF. Comparison of the z = 7.0 Lyα LF to the one predicted by an LAE evolution model further reveals that galaxy evolution alone cannot explain all of the decline of the Lyα LF. If we attribute the discrepancy to Lyα attenuation by neutral hydrogen, the intergalactic medium transmission of Lyα photons at z = 7.0 would be {T}_{Lyα }^{IGM}≤slant 0.6{--}0.7. It is lower (higher) than the {T}_{Lyα }^{IGM} at z = 6.6 (7.3) derived by previous studies, suggesting rapid increase in neutral fraction at z &gt; 6. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan....

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z &gt; 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 &lt; z &lt; 8 for [C II] line emission and reach a limiting luminosity of L _{[C II]} ̃ (1.6-2.5) × 10⁸ L _☉. We identify 14 [C II] line emitting candidates in this redshift range with significances &gt;4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S _{1.2 mm} = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M _☉ yr^-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L _{[C II]} versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 &lt; z &lt; 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe....

We present the KMOS^3D survey, a new integral field survey of over 600 galaxies at 0.7 &lt; z &lt; 2.7 using KMOS at the Very Large Telescope. The KMOS^3D survey utilizes synergies with multi-wavelength ground- and space-based surveys to trace the evolution of spatially resolved kinematics and star formation from a homogeneous sample over 5 Gyr of cosmic history. Targets, drawn from a mass-selected parent sample from the 3D-HST survey, cover the star formation-stellar mass (M _*) and rest-frame (U - V) - M _* planes uniformly. We describe the selection of targets, the observations, and the data reduction. In the first-year of data we detect Hα emission in 191 M _* = 3 × 10⁹-7 × 10¹¹ M _☉ galaxies at z = 0.7-1.1 and z = 1.9-2.7. In the current sample 83% of the resolved galaxies are rotation dominated, determined from a continuous velocity gradient and v _rot/σ₀ &gt; 1, implying that the star-forming "main sequence" is primarily composed of rotating galaxies at both redshift regimes. When considering additional stricter criteria, the Hα kinematic maps indicate that at least ~70% of the resolved galaxies are disk-like systems. Our high-quality KMOS data confirm the elevated velocity dispersions reported in previous integral field spectroscopy studies at z &gt;~ 0.7. For rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s^-1at z ~ 2.3 to 25 km s^-1at z ~ 0.9. Combined with existing results spanning z ~ 0-3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally stable disk theory. Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDS 092A-0091, 093.A-0079)....