Galaxy formation and evolution

Abstract:

ABSTRACT Recent studies of gas kinematics at high redshift have reported discy systems that appear to challenge models of galaxy formation, but it is unclear whether they are representative of the underlying galaxy population. We present the first statistical sample of spatially resolved ionized gas kinematics at high redshift, comprised of 213 H $\alpha$ emitters in GOODS-S and GOODS-N at redshifts $z\approx 3.9\!-\!6.5$, observed with James Webb Space Telescope/NIRCam slitless spectroscopy and imaging from JADES, FRESCO, and CONGRESS. The sample probes two orders of magnitude in stellar mass ($\log (M_{\star }[\mathrm{M}_{\odot }])\approx 8\!-\!10$) and star formation rate ($\text{SFR}\approx 0.3\!-\!100\, \mathrm{M}_{\odot }\, \mathrm{yr}^{-1}$), and is representative down to $\log (M_{\star }[\mathrm{M}_{\odot }])\approx 9$. Using a novel inference tool, geko, we model the grism data to measure morphological and kinematic properties of the ionized gas, as probed by H $\alpha$. Our results are consistent with a decrease of the rotational support $v/\sigma _0$ and increase of the velocity dispersion $\sigma _0$ with redshift, when compared to $z< 3$, with $\sigma _0\approx 100$ km s$^{-1}$ and $v/\sigma _0\approx 1\!-\!2$ at $z\approx 3.9\!-\!6.5$. We study the relations between $\sigma _0$ and $v/\sigma _0$, and different star formation tracers and find a large scatter and diversity, with the most significant correlation between $\sigma _0$ and SFR. We find no evolution of the fraction of rotationally supported systems ($v/\sigma _0>1$) from $z\sim 5.5$ to $z\sim 4.5$, measured at $f=(34\pm 5){{\ \rm per\ cent}}$ in both redshift bins, for galaxies with masses $9<\log (M_{\star }[\mathrm{M}_{\odot }])< 10$. Overall, discs do not dominate the turbulent high-redshift galaxy population in the mass range probed by this work, but they remain a sizeable population. When placed in the context of studies up to cosmic noon, our results are consistent with a needed increase of disc-like systems with cosmic time.

Abstract:

Current co-evolutionary models of galaxies and their supermassive black holes (SMBHs) almost unanimously predict the existence of a heavily dust-obscured nuclear phase, critical in growing the SMBH and providing feedback to the host galaxy. However, this phase is poorly understood. Compact obscured nuclei (CONs) are relatively common in local (ultra-)luminous infrared galaxies and are the most obscured nuclei known to date, offering the opportunity to study the effects of such a dust-obscured phase on the galaxy. This work presents a case study of the local CON Zw049.057; we study the large-scale features of the galaxy and their connection to the ongoing activity of the central CON. We present new, targeted MUSE observations of the local CON galaxy Zw049.057, which is known to host multiple outflow features within its central few hundred parsecs. By mapping the kinematics of Hα, we analysed the large-scale features of the galaxy. For the first time, we identify a kiloparsec-scale ionised outflow in Zw049.057, traced by Hα emission. Kinematics reveal the outflow to be blueshifted and orientated to the foreground of the stellar disk. The ionisation of this outflow is consistent with shock-heating, which may be related to the presence of a previously identified radio jet in the galaxy.

Abstract:

Abstract We extract with ppxf and analyse the high-order stellar kinematic moments h3 (related to skewness) and h4 (related to kurtosis) in a complete subsample of 2230 galaxies with well-sampled line-of-sight velocity distributions (σe ≳ 140 km/s) from the final data release of 10010 unique galaxies of the MaNGA survey. To reduce template mismatch, we created a stellar library based on MaStar. We used proxies for the specific angular momentum parameter ($\lambda _{R_\mathrm{e}}$) and ellipticity (ϵ) to distinguish between fast and slow rotators. Using the Pearson correlation coefficient between spatially resolved h3 and V/σ within the isophotes of 2.5 half-light radii (Re), we classified 1,599 fast rotators into: (i) 1,073 galaxies showing a strong h3 versus V/σ anti-correlation, indicative of normal rotating stellar disks as observed in earlier studies. (ii) 526 galaxies exhibiting weak or no correlation between h3 and V/σ. These galaxies are likely disturbed, showing signs of bars or merging. Further inspection revealed that 85 galaxies from the latter group contain an anti-correlated inner disk, with half of these inner disks composed of younger stellar populations, indicative of recent gas accretion and nuclear star formation. This catalogue presents measurements of high-order stellar kinematic moments, providing a basis for exploring their potential links with the kinematic structures of galaxies. We have made the newly extracted high-order kinematics publicly available for further studies on stellar dynamics and galaxy formation.