The recently-developed J-region Asymptotic Giant Branch (JAGB) method has extraordinary potential as an extragalactic standard candle, capable of calibrating the absolute magnitudes of locally-accessible Type Ia supernovae, thereby leading to an independent determination of the Hubble constant. Using Gaia Early Data Release 3 (EDR3) parallaxes, we calibrate the zeropoint of the JAGB method, based on the mean luminosity of a color-selected subset of carbon-rich AGB stars. We identify Galactic carbon stars from the literature and use their near-infrared photometry and Gaia EDR3 parallaxes to measure their absolute J-band magnitudes. Based on these Milky Way parallaxes we determine the zeropoint of the JAGB method to be M_J = -6.14 +/- 0.05 (stat) +/- 0.11 (sys) mag. This Galactic calibration serves as a consistency check on the JAGB zeropoint, agreeing well with previously-published, independent JAGB calibrations based on geometric, Detached-Eclipsing Binary (DEB) distances to the LMC and SMC. However, the JAGB stars used in this study suffer from the high parallax uncertainties that afflict the bright and red stars in EDR3, so we are not able to attain the higher precision of previous calibrations, and ultimately will rely on future improved DR4 and DR5 releases.
We present an absolute calibration of the J-region Asymptotic Giant Branch (JAGB) method using published photometry of resolved stars in 20 nearby galaxies observed with HST using the WFC3-IR camera and the F110W (Broad J-Band) filter. True distance moduli for each of the galaxies are based on the Tip of the Red Giant Branch (TRGB) method as uniformly determined by Dalcanton et al. (2012). From a composite color-magnitude diagram composed of over 6 million stars, leading to a sample of 453 JAGB stars in these galaxies, we find M_{F110W}{JAGB} = -5.77 +/- 0.02 mag(statistical error on the mean)…
We apply the near-infrared J-region Asymptotic Giant Branch (JAGB) method, recently introduced by Madore \& Freedman (2020), to measure the distances to 14 nearby galaxies out to 4 Mpc. We use the geometric detached eclipsing binary (DEB) distances to the LMC and SMC as independent zero-point calibrators. We find excellent agreement with previously published distances based on the Tip of the Red Giant Branch (TRGB): the JAGB distance determinations (including the LMC and SMC) agree in the mean to within Delta(JAGB-TRGB) = +0.025 +/- 0.013 mag, just over 1%, where the TRGB I-band zero point is …
A method to search for tidal streams and to fit their orbits based on maximum likelihood is presented and applied to the Gaia data. Tests of the method are performed showing how a simulated stream produced by tidal stripping of a star cluster is recovered when added to a simulation of the Gaia catalogue. The method can be applied to search for streams associated with known progenitors or to do blind searches in a general catalogue. As the first example, we apply the method to the globular cluster M68 and detect its clear tidal stream stretching over the whole North Galactic hemisphere, and pas…
Classical Cepheids in open clusters are key ingredients for stellar population studies and the characterization of variable stars, as they are tracers of young and massive populations and of recent star formation episodes. Cluster Cepheids are of particular importance since they can be age dated by using the cluster's stellar population to obtain the Cepheid period-luminosity-age relation. In this contribution, we present the preliminary results of an all-sky search for classical Cepheids in Galactic open clusters by taking advantage of the unprecedented astrometric precision of the second dat…
The Integral Shaped Filament (ISF) is the nearest molecular cloud with rapid star formation, including massive stars, and it is therefore a star-formation laboratory. We use Gaia parallaxes, to show that the distances to young Class II stars ('disks') projected along the spine of this filament are related to the gas radial velocity by $$ v = -{D\overτ} + K;\qquad τ= 4\,{\rm Myr}, $$ where $K$ is a constant. This implies that the ISF is a standing wave, which is consistent with the Stutz & Gould (2016) 'Slingshot' prediction. The $τ=4\,{\rm Myr}$ timescale is consistent with the 'Slingshot' pic…
We describe a homogeneous catalog compilation of common proper motion stars based on Gaia DR2. A preliminary list of all pairs of stars within the radius of 100 pc around the Sun with a separation less than a parsec was compiled. Also, a subset of comoving pairs, wide binary stars, was selected. The clusters and systems with multiplicity larger than 2 were excluded from consideration. The resulting catalog contains 10358 pairs of stars. The catalog selectivity function was estimated by comparison with a set of randomly selected field stars and with a model sample obtained by population synthes…
CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台光学天文重点实验室）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与空间科学学院前沿交叉研究院）
Gaia's Early Third Data Release (EDR3) does not contain new radial velocities because these will be published in Gaia's full third data release (DR3), expected in the first half of 2022. To maximise the usefulness of EDR3, Gaia's second data release (DR2) sources (with radial velocities) are matched to EDR3 sources to allow their DR2 radial velocities to also be included in EDR3. This presents two considerations: (i) arXiv:1901.10460 (hereafter B19) published a list of 70,365 sources with potentially contaminated DR2 radial velocities; and (ii) EDR3 is based on a new astrometric solution and a…
Binarity and beyond in A stars I. Survey description and first results of VLTI/GRAVITY observations of VAST targets with high Gaia-Hipparcos accelerations
This work studies the candidate double and multiple open clusters (OCs) in the galactic sector from l = 240o to l = 270o, which contains the Vela-Puppis star formation region. To do that, we have searched the most recent and complete catalogues of OCs by hand to get an extensive list of 22 groups of OCs involving 80 candidate members. Gaia EDR3 has been used to review some of the candidate OCs and look for new OCs near the candidate groups. Gaia data also permitted filtering out most of the field sources that are not member stars of the OCs. The plotting of combined colour-magnitude diagrams o…
We present photometry of 30 Galactic RR Lyrae variables taken with HST WFC3/IR for the Carnegie-Chicago Hubble Program. These measurements form the base of the distance ladder measurements that comprise a pure Population II base to a measurement of Ho at an accuracy of 3%. These data are taken with the same instrument and filter (F160W) as our observations of RR Lyrae stars in external galaxies so as to to minimize sources of systematic error in our calibration of the extragalactic distance scale. We calculate mean magnitudes based on one to three measurements for each RR Lyrae star using star…
