Galaxy formation and evolution

Abstract:

Untargeted neutral hydrogen ( > 1.5 kpc) to be ultra-diffuse galaxies (UDGs). Furthermore, we extracted surveys are well suited to identifying low surface brightness galaxies (LSBGs) that are gas rich, and they offer a complementary view to optically selected populations. We examined the LSBG population as identified via stellar and gaseous content using the MIGHTEE XMM-LSS early science data and the publicly available catalogs of optically identified LSBGs. There is currently little overlap between these datasets, with only three galaxies commonly detected. We performed surface brightness photometry of selected MIGHTEE detections to find 29 LSBGs, and 26 of these meet the size requirement (R_ eff spectra at the location of all optically identified galaxies, placing upper limits on the mass ratio in these systems. While the population overall tends toward bluer colors, the and the optically selected samples mostly overlap in mean effective surface brightness, effective radii, and color. Although it is not straightforward to discern why the LSBGs were missed in optical searches, this work highlights the utility of surveys in finding these faint systems. The LSBGs are gas rich compared to the general population. Furthermore, three out of four UDGs with available kinematics show no systematic offset from the baryonic Tully-Fisher relation, although we are biased away from sources with low rotational velocities due to the low spectral resolution of the data. This work demonstrates the utility of observations for finding and characterizing the low surface brightness Universe.

Abstract:

Luminous infrared (IR) galaxies are key sites of obscured stellar mass assembly at z > 0.5. Their star formation rates (SFRs) are often estimated using the luminosities of the 6.2 and 11.2 μm polycyclic aromatic hydrocarbon (PAH) features or those of the [Ne ii] and [Ne iii] fine-structure lines, as they are minimally affected by obscuration. It is uncertain whether the calibration of these features as SFR tracers depends on the starburst bolometric luminosity or the level of active galactic nucleus (AGN) activity. We here investigate the relationship between the luminosities of PAH and neon lines with SFR for highly luminous objects using radiative transfer modeling and archival observations of 42 local ultraluminous (≥1012L⊙) IR galaxies (ULIRGs). We find that PAH and [Ne ii] features arise mainly in star-forming regions, with small contributions from the AGN or host, but that the [Ne iii] line has a mixed contribution from both star formation and AGN activity. We present relations between LPAH and L[Ne II], and both starburst luminosity and SFR. We find relations for lower-luminosity (LIR ≃ 1010–1012L⊙) systems underestimate the SFRs in local ULIRGs by up to ∼1 dex. The 6.2 and 11.2 μm PAH features, and the [Ne ii] line, are thus good tracers of SFR in ULIRGs. We do not find that a more luminous AGN affects the relationship between SFR and PAH or neon luminosity but that it can make PAH emission harder to discern. Our results and derived relations are relevant to studies of star-forming and composite galaxies at z < 3 with the James Webb Space Telescope.

Abstract:

We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M* > 1010 M⊙over 0.5 < z < 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii (Re) of the galaxies at rest-frame 0.3, 0.5, and 1 μm. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μm than they are at 0.3 μm (0.5 μm). Regardless of wavelengths, the Re of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M* = 1010–1010.6 M⊙, the evolution follows Re ∝ (1 + z)−1.1, whereas it becomes steeper, following Re ∝ (1 + z)−1.7, for higher-mass quiescent galaxies with M* > 1010.6 M⊙. To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between Re and the formation redshift (zform) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with Re∝(1+zform)−1 , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between Re and zform depends on stellar age. Older quiescent galaxies have a steeper relationship between Re and zform than that expected from the progenitor effect alone, suggesting that mergers and/or post-quenching continuous gas accretion drive additional size growth in very massive systems. We find that the z > 3 quiescent galaxies in our sample are very compact, with mass surface densities Σe ≳ 1010 M⊙ kpc−2, and their Re are possibly even smaller than anticipated from the size evolution measured for lower-redshift quiescent galaxies. Finally, we take a close look at the structure of GS-9209, one of the earliest confirmed massive quiescent galaxies at zspec ∼ 4.7. From UV to NIR, GS-9209 becomes increasingly compact, and its light profile becomes more spheroidal, showing that the color gradient is already present in this earliest massive quiescent galaxy.