- This paper used mock observations of CII and Ha based on SERRA simulations to study the kinematics of star-forming galaxies with M* > 10^8 M_sun at z~4-9, in particular focusing on the velocity to dispersion ratios (V/sigma).
- Regarding the differences between the kinematics of CII and Ha, the authors found that the sigma from Ha increases with M* steeper than the sigma from CII. They attribute the higher sigma of Ha to the inclusion of extraplanar ionized gas that may be due to outflows.
- They reported that ~60% of the whole sample of 3218 galaxies are dynamically cold disks, with V/sigma from CII between 4-10.
- Surprisingly, they did not find any evolution of V/sigma from both tracers with redshift from z~4-9 (see the figure). Their V/sigma of CII looks higher than the majority of the CII observations (triangles) for z > 5, although they attribute that to the overestimated sigma from the real but low-resolution observations. Their V/sigma from Ha are also higher than the observations (square symbols), and the TNG50 simulations at z ~5.
Summary: The paper discusses the search for CO and other molecules in emission and absorption in front of a sample of 30 targets, comprising 16 “associated” and 14 “intervening” HI 21-cm absorbers. The observations were done with the IRAM-30m telescope, simultaneously at 3mm and 2mm, exploring several lines of the CO ladder and HCO+, according to the redshift. Eight targets have been detected in emission, of which five are new. The derived molecular gas masses range from 10^9 to 7×10^11 M⊙2. The authors also report four new detections in absorption. Two of the associated CO absorption line detections at high redshift (z=1.211 and 1.275) resulted from the high spatial resolution follow-up with NOEMA. The disparity between the mm molecular and HI 21-cm absorption lines for these and another intervening system detected in HNC at z=1.275, is attributable to radio and mm sight lines tracing different media. The authors indicate that two distinct phases exist: one near galaxy centers with a larger CO-to-HI abundance ratio, and another with lower molecular abundance in the outer regions of the galaxy. The detection of absorption requires sufficient spatial resolution to overcome the dilution by emission, which will be an important criterion for mm follow-up of 21-cm absorbers from ongoing large-scale surveys.
Summary: Le Conte et al. analysed galaxies between redshift 1<z<3 in the CANDELS fields, using JWST NIRCam and HST WFC3 imaging, to investigate the presence of bars in disk galaxies at cosmic noon. Using the CEERS observations, they identify the galaxies with photometric redshift in the range of interest, and select the galaxies with good enough spatial resolution for the analysis, bringing the sample to a final number of 768 galaxies. Repeating a similar process with HST imaging of the same regions, they have a sample of 115 HST detected galaxies. The authors then look at the disk fraction in their main sample, through visual inspection of the cutouts by two of the co-authors, and find a disk fraction of about 40%, in line with morphological studies by Ferreira et al. 2023. Finally, they classify the galaxies in both the HST and JWST samples as non-barred, weakly barred or strongly barred; again through visual inspection by five of the co-authors. The analysis is done using the F444W filter for the main sample, and repeated with the F356W filter, with no noticeable change in bar fractions; and is done on the HST sample using the F160W filter. The final bar fractions reported for the JWST sample are 19% in the 1<z<2 range and ~7% in the 2<z<3 range, 3-4 times larger than for the HST sample (results shown in Fig. 6). They find, in line with previous studies, a decreasing trend of the bar fraction with redshift, but that the wavelength chosen for the analysis will impact the results greatly. They also assess that due to the limits in resolution, their results are biased towards larger bars (>2.5-3kpc), and thus their results are most probably lower limits on the bar fraction. Finally, they argue that the amount of bars in galaxies above z=2 points towards a much earlier appearance of bars in disk galaxies than previously thought.
In this paper the authors present the spectroscopic analysis of 8 ultra-faint lensed galaxies at 6<z<8, using a combination of HST, JWST imaging (NIRCam, from the UNCOVER survey), and deep NIRSPec spectroscopy (also from UNCOVER). Given the high magnification and long integration then manage to reach unprecedentedly faint magnitudes. Using mostly the Halpha line they compute the ionizing efficiency of the faint population at the epoch of reionization. Combined with a computation of the UV photons density they show that a low escape fraction of 5% could be sufficient to ionize the universe, and that faint galaxies (i.e. the bulk of the galaxy population) are prodigous producer of ionizing photons. According to them this shows that faint galaxies were the main drivers of cosmic reionization.
This study compared 110 interacting galaxies with 126 isolated galaxies with IFU + CO observations of central ~1Re of local galaxies.
They found that the gas fraction increases in the interacting galaxies compared to the isolated galaxies in their sample, but SFE and sSFR do not increase.
They compared the relative importance of gas fraction and SFE in each sSFR bin, and concluded that in most of cases in interacting galaxies, changes in SFE is more likely the main driver for the variations of sSFR.
Introduces a method to estimate stellar half-mass radii for galaxies at 0.5 < z < 2.5, utilising integrated UV-to-midIR photometric data.
Validates the method by comparing their estimates with measurements from JWST/NIRCam imaging for a subset of CEERS galaxies, showing excellent agreement with small systematic offsets and scatter within the error budget.
Examines the effect of projection using a deprojection technique that considers the shape distribution of galaxies, their dependencies on stellar mass and redshift, and concludes that deprojection has little impact on the size-mass distribution.
Reveals that the size-mass distribution of galaxies at 0.5 < z < 1.5 is less steep in the rest-frame optical than previously believed, primarily due to the influence of massive star-forming galaxies.
Offers a straightforward conversion from light-to-stellar mass-weighted sizes, making it valuable for galaxies lacking spatially resolved near-IR imaging or at high z.
Acknowledges uncertainties in small galaxies, challenging due to limited understanding of the near-IR PSF of NIRCam.
Summary: This paper analyze the detailed kinematic features of MUSE data cube of the inner starburst ring of NGC 1097. They emphasize the difficulties of reviewing the inflow features by simply comparing the gas velocity map with the circular disk model, due to both the uncertainties of the prior information of the PA and inclination and the presumably complex kinematics of the gas dynamics. Then, they discuss the evidence of the physical origin of some coherent velocity map residual patterns with BPT diagram and advertise that the velocity difference between [NII] and Halpha lines can be a useful indicator of the shocked region of the inflow gas. Overall, this work focuses on very small scale gas kinematic structures comparing to the studies of high-z galaxies of our group.
Summary: Zhang et al look at 61 galaxies between z=5.4 and 8.9, both using NIRSpec spectroscopy and NIRCam imaging, to study the outflow properties in their sample. They make a study of both spatially extended [OIII] emission in the imaging (5/61) and broad component in the emission line, indicating the presence of fast winds (5/30); including one galaxy that has both spatially extended emission and a broad component in the spectra. They compute the ratio of the wind velocity over the escape velocity of the galaxies' halo, and find that none of the detected outflows have velocities high enough to eject gas outside the gravitational well of the halo. They conjecture that they are witnessing the different phases of a star forming outflow event (as shown in the figure, where in the beginning outflows can only be seen in the spectra, then an extended emission is observed, and finally it falls back into the galaxy). They also compare their outflow incidence in the extended emission at high redshift to local studies, and find an increase in the incidence broadly consistent with the increase in major merger rate; but fail to observe a similar increase in incidence with the "spectral" outflows (Figure 11).
Summary: The authors observed wide rest-UV absorption lines in three MOSDEF galaxies. They argue that these are the signature of inflowing gas from the recycled metal-enriched gas with a large velocity ~250-500 km/s, instead of pristine gas from the CGM.
