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Abstract We have used the Atacama Large Millimeter/submillimeter Array to map CO(3–2) emission from a galaxy, DLA-B1228g, associated with the high-metallicity damped Lyαabsorber atz≈ 2.1929 toward the QSO PKS B1228–113. At an angular resolution of ≈0.″32 × 0.″24, DLA-B1228g shows extended CO(3–2) emission with a deconvolved size of ≈0.″78 × 0.″18, i.e., a spatial extent of ≈6.4 kpc. We detect extended stellar emission from DLA-B1228g in a Hubble Space Telescope Wide Field Camera 3 F160W image and find that Hαemission is detected in a Very Large Telescope SINFONI image from only one side of the galaxy. While the clumpy nature of the F160W emission and the offset between the kinematic and physical centers of the CO(3–2) emission are consistent with a merger scenario, this appears unlikely due to the lack of strong Hαemission, the symmetric double-peaked CO(3–2) line profile, the high molecular gas depletion timescale, and the similar velocity dispersions in the two halves of the CO(3–2) image. Kinematic modeling reveals that the CO(3–2) emission is consistent with arising from an axisymmetric rotating disk with an exponential profile, a rotation velocity ofv_rot= 328 ± 7 km s⁻¹, and a velocity dispersion ofσ_v= 62 ± 7 km s⁻¹. The high value of the ratiov_rot/σ_v, ≈5.3, implies that DLA-B1228g is a rotation-dominated cold disk galaxy, the second case of a high-zHi-absorption-selected galaxy identified with a cold rotating disk. We obtain a dynamical mass ofM_dyn= (1.5 ± 0.1) × 10¹¹M_⊙, similar to the molecular gas mass of ≈10¹¹M_⊙inferred from earlier CO(1–0) studies; this implies that the galaxy is baryon-dominated in its inner regions. 

ABSTRACT Localization of fast radio bursts (FRBs) to arcsecond and subarcsecond precision maximizes their potential as cosmological probes. To that end, FRB detection instruments are deploying triggered complex-voltage capture systems to localize FRBs, identify their host galaxy, and measure a redshift. Here, we report the discovery and localization of two FRBs (20220717A and 20220905A) that were captured by the transient buffer system deployed by the MeerTRAP instrument at the MeerKAT telescope in South Africa. We were able to localize the FRBs to precision of $$\sim$$1 arcsecond that allowed us to unambiguously identify the host galaxy for FRB 20220717A (posterior probability $$\sim$$0.97). FRB 20220905A lies in a crowded region of the sky with a tentative identification of a host galaxy but the faintness and the difficulty in obtaining an optical spectrum preclude a conclusive association. The bursts show low linear polarization fractions (10–17 per cent) that conform to the large diversity in the polarization fraction observed in apparently non-repeating FRBs akin to single pulses from neutron stars. We also show that the host galaxy of FRB 20220717A contributes roughly 15 per cent of the total dispersion measure (DM), indicating that it is located in a plasma-rich part of the host galaxy which can explain the large rotation measure. The scattering in FRB 20220717A can be mostly attributed to the host galaxy and the intervening medium and is consistent with what is seen in the wider FRB population. 

Abstract The discovery and localization of FRB 20240209A by the Canadian Hydrogen Intensity Mapping Fast Radio Burst (CHIME/FRB) experiment marks the first repeating FRB localized with the CHIME/FRB Outriggers and adds to the small sample of repeating FRBs with associated host galaxies. Here we present Keck and Gemini observations of the host that reveal a redshiftz = 0.1384 ± 0.0004. We perform stellar population modeling to jointly fit the optical through mid-IR data of the host and infer a median stellar mass log(M_*/M_⊙) = 11.35 ± 0.01 and a mass-weighted stellar population age  ~11 Gyr, corresponding to the most massive and oldest FRB host discovered to date. Coupled with a star formation rate  <0.31M_⊙yr⁻¹, the specific star formation rate  <10^−11.9yr⁻¹classifies the host as quiescent. Through surface brightness profile modeling, we determine an elliptical galaxy morphology, marking the host as the first confirmed elliptical FRB host. The discovery of a quiescent early-type host galaxy within a transient class predominantly characterized by late-type star-forming hosts is reminiscent of short-duration gamma-ray bursts, Type Ia supernovae, and ultraluminous X-ray sources. Based on these shared host demographics, coupled with a large offset as demonstrated in our companion Letter, we conclude that preferred sources for FRB 20240209A include magnetars formed through merging binary neutron stars/white dwarfs or the accretion-induced collapse of a white dwarf, or a luminous X-ray binary. Together with FRB 20200120E localized to a globular cluster in M81, our findings provide strong evidence that some fraction of FRBs may arise from a process distinct from the core collapse of massive stars.