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We measure the properties of optical emission lines in multiple locations across the Large Magellanic Cloud (LMC) using the Australian National University 2.3-m telescope and the Wide-Field Spectrograph (WiFeS). From these measurements, we interpolate maps of the gas-phase metallicity, extinction, Hα radial velocity, and Hα velocity dispersion across the LMC. The LMC metallicity maps show a complex structure that cannot be explained by a simple radial gradient. The bright H ii region 30 Doradus stands out as a region of high extinction. The Hα and H i gas radial velocities are mostly consistent except for a region to the south and east of the LMC centre. The Hα velocity dispersion is almost always higher than the H i velocity dispersion, except in the region that shows the divergence in radial velocity, where the H i velocity dispersion is greater than the Hα velocity dispersion. This suggests that the H i gas is diverging from the stellar radial velocity, perhaps as a result of inflow or outflow of H i gas. The study of dwarf galaxies like the LMC is important as they are the building blocks of larger galaxies like our own Milky Way. The maps provided in this work show details not accessible in the study of more distant dwarf galaxies.

 

The origin of the radio emission in radio-quiet quasars (RQQ) is not established yet. We present new VLBA observations at 1.6 and 4.9 GHz of 10 RQQ (9 detected), which together with published earlier observations of 8 RQQ (5 detected), forms a representative sample of 18 RQQ drawn from the Palomar–Green sample of low z (< 0.5) AGN. The spectral slope of the integrated emission extends from very steep (α < −1.98) to strongly inverted (α = +2.18), and the slopes of 9 of the 14 objects are flat (α > −0.5). Most objects have an unresolved flat-spectrum core, which coincides with the optical Gaia position. The extended emission is generally steep-spectrum, has a low brightness temperature (< 107 K), and is displaced from the optical core (the Gaia position) by ∼ 5–100 pc. The VLBA core flux is tightly correlated with the X-ray flux, and follows a radio to X-ray luminosity relation of log LR/LX ≃ −6, for all objects with a black hole mass log MBH/M⊙ < 8.5. The flatness of the core emission implies a compact source size (≲ 0.1 pc), which likely originates from the accretion disc corona. The mas-scale extended emission is optically thin and of clumpy structure, and is likely produced by an outflow from the center. Radio observations at higher frequencies can further test the accretion disc coronal emission interpretation for the core emission in RQQ.

 

An unprecedented array of new observational capabilities are starting to yield key constraints on models of the epoch of first light in the Universe. In this Letter we discuss the implications of the UV radiation background at cosmic dawn inferred by recent JWST observations for radio experiments aimed at detecting the redshifted 21 cm hyperfine transition of diffuse neutral hydrogen. Under the basic assumption that the 21 cm signal is activated by the Lyαphoton field produced by metal-poor stellar systems, we show that a detection at the low frequencies of the EDGES and SARAS3 experiments may be expected from a simple extrapolation of the declining UV luminosity density inferred atz≲ 14 from JWST early galaxy data. Accounting for an early radiation excess above the cosmic microwave background suggests a shallower or flat evolution to simultaneously reproduce low- and high-zcurrent UV luminosity density constraints, which cannot be entirely ruled out, given the large uncertainties from cosmic variance and the faint-end slope of the galaxy luminosity function at cosmic dawn. Our findings raise the intriguing possibility that a high star formation efficiency at early times may trigger the onset of intense Lyαemission at redshiftz≲ 20 and produce a cosmic 21 cm absorption signal 200 Myr after the Big Bang.

 

Abstract We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST, and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local ( z < 0.1) early-type red geyser galaxies. These galaxies have a low star formation activity (with a star formation rate, SFR, ∼ 0.01 M ⊙ yr −1 ), but show unique extended patterns in spatially resolved emission-line maps that have been interpreted as large-scale ionized winds driven by active galactic nuclei (AGN). In this work, we confirm that red geysers host low-luminosity radio sources ( L 1.4GHz ∼ 10 22 WHz −1 ). Out of 42 radio-detected red geysers, 32 are spatially resolved in LoTSS and FIRST, with radio sizes varying between ∼5–25 kpc. Three sources have radio sizes exceeding 40 kpc. A majority display a compact radio morphology and are consistent with either low-power compact radio sources (FR0 galaxies) or radio-quiet quasars. They may be powered by small-scale AGN-driven jets that remain unresolved at the current 5″ resolution of radio data. The extended radio sources, not belonging to the “compact” morphological class, exhibit steeper spectra with a median spectral index of −0.67, indicating the dominance of lobed components. The red geysers hosting extended radio sources also have the lowest specific SFRs, suggesting they either have a greater impact on the surrounding interstellar medium or are found in more massive halos on average. The degree of alignment of the ionized wind cone and the extended radio features are either 0° or 90°, indicating possible interaction between the interstellar medium and the central radio AGN. 

Abstract This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.