- Publication Date:
- NSF-PAR ID:
- 10349772
- Journal Name:
- The Astronomical Journal
- Volume:
- 163
- Issue:
- 2
- Page Range or eLocation-ID:
- 47
- ISSN:
- 0004-6256
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We present new empirical infrared period–luminosity–metallicity (PLZ) and period–Wesenheit–metallicity (PWZ) relations for RR Lyae based on the latest Gaia Early Data Release 3 (EDR3) parallaxes. The relations are provided in the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands, as well as in the W(W1,
V − W1) and W(W2,V − W2) Wesenheit magnitudes. The relations are calibrated using a very large sample of Galactic halo field RR Lyrae stars with homogeneous spectroscopic [Fe/H] abundances (over 1000 stars in the W1 band), covering a broad range of metallicities (−2.5 ≲ [Fe/H] ≲ 0.0). We test the performance of our PLZ and PWZ relations by determining the distance moduli of both galactic and extragalactic stellar associations: the Sculptor dwarf spheroidal galaxy in the Local Group (finding ), the Galactic globular clusters M4 ( ), and the Reticulum globular cluster in the Large Magellanic Cloud ( ). The distance moduli determined through all our relations are internally self-consistent (within ≲0.05 mag) but are systematically smaller (by ∼2–3σ ) than previous literature measurements taken from a variety of methods/anchors. However, a comparison with similar recent RR Lyrae empirical relations anchored with EDR3 likewise shows, to varyingmore » -
ABSTRACT Extremely red quasars (ERQs) are an interesting sample of quasars in the Baryon Oscillation Spectroscopic Sample (BOSS) in the redshift range of 2.0–3.4 and have extreme red colours of i − W3 ≥ 4.6. Core ERQs have strong C iv emission lines with rest equivalent width of ≥100 Å. Many core ERQs also have C iv line profiles with peculiar boxy shapes which distinguish them from normal blue quasars. We show, using a combination of kernel density estimation and local outlier factor analyses on a space of the i − W3 colour, C iv rest equivalent width and line kurtosis, that core ERQs likely represent a separate population rather than a smooth transition between normal blue quasars and the quasars in the tail of the colour-REW distribution. We apply our analyses to find new criteria for selecting ERQs in this 3D parameter space. Our final selection produces 133 quasars, which are three times more likely to have a visually verified C iv broad absorption line feature than the previous core ERQ sample. We further show that our newly selected sample are extreme objects in the intersection of the WISE AGN catalogue with the MILLIQUAS quasar catalogue in the colour–colour space of (W1 − W2, W2 − W3). Thismore »
-
Abstract We present PHANGS–ALMA, the first survey to map CO J = 2 → 1 line emission at ∼1″ ∼100 pc spatial resolution from a representative sample of 90 nearby ( d ≲ 20 Mpc) galaxies that lie on or near the z = 0 “main sequence” of star-forming galaxies. CO line emission traces the bulk distribution of molecular gas, which is the cold, star-forming phase of the interstellar medium. At the resolution achieved by PHANGS–ALMA, each beam reaches the size of a typical individual giant molecular cloud, so that these data can be used to measure the demographics, life cycle, and physical state of molecular clouds across the population of galaxies where the majority of stars form at z = 0. This paper describes the scientific motivation and background for the survey, sample selection, global properties of the targets, Atacama Large Millimeter/submillimeter Array (ALMA) observations, and characteristics of the delivered data and derived data products. As the ALMA sample serves as the parent sample for parallel surveys with MUSE on the Very Large Telescope, the Hubble Space Telescope, AstroSat, the Very Large Array, and other facilities, we include a detailed discussion of the sample selection. We detail the estimationmore »
-
Abstract Nuclear rings are excellent laboratories for studying intense star formation. We present results from a study of nuclear star-forming rings in five nearby normal galaxies from the Star Formation in Radio Survey (SFRS) and four local LIRGs from the Great Observatories All-sky LIRG Survey at sub-kiloparsec resolutions using Very Large Array high-frequency radio continuum observations. We find that nuclear ring star formation (NRSF) contributes 49%–60% of the total star formation of the LIRGs, compared to 7%–40% for the normal galaxies. We characterize a total of 57 individual star-forming regions in these rings, and find that with measured sizes of 10–200 pc, NRSF regions in the LIRGs have star formation rate (SFR) and Σ SFR up to 1.7 M ⊙ yr −1 and 402 M ⊙ yr −1 kpc −2 , respectively, which are about 10 times higher than in NRSF regions in the normal galaxies with similar sizes, and comparable to lensed high- z star-forming regions. At ∼100–300 pc scales, we estimate low contributions (<50%) of thermal free–free emission to total radio continuum emission at 33 GHz in the NRSF regions in the LIRGs, but large variations possibly exist at smaller physical scales. Finally, using archival sub-kiloparsec resolution COmore »