arXiv:1807.11496 - Gaia: Orion's Integral Shaped Filament is a Standing Wave

Paper: Gaia: Orion's Integral Shaped Filament is a Standing Wave
Authors: Amelia M. Stutz, Valentina I. Gonzalez-Lobos, Andrew Gould

Abstract: 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=−Dτ+K;τ=4Myr,

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=4Myr timescale is consistent with the 'Slingshot' picture that the Orion Nebula Cluster (ONC) is the third cluster to be violently split off from the Orion A cloud (following NGC 1981 and NGC 1987) at few-Myr intervals due to gravito-magnetic oscillations. We also present preliminary evidence that the truncation of the ISF is now taking place 16′ south of the ONC and is mediated by a torsional wave that is propagating south with a characteristic timescale τtorsion=0.5Myr, i.e. eight times shorter. The relation between these two wave phenomena is not presently understood.

My Comment: Dear students: this (one reason) why it is important to understand simple waves. 

My Scrawling Notes:

arXiv:1807.06368 -- Planetary Nebulae distances in GAIA DR2

Paper: Planetary Nebulae distances in GAIA DR2
Authors: Stefan Kimeswenger, Daniela Barría

Abstract: Context: Planetary Nebula distance scales often suffer for model dependent solutions. Model independent trigonometric parallaxes have been rare. Space based trigonometric parallaxes are now available for a larger sample using the second data release of GAIA. 

Aims: We aim to derive a high quality approach for selection criteria of trigonometric parallaxes for planetary nebulae and discuss possible caveats and restrictions in the use of this data release. 

Methods: A few hundred sources from previous distance scale surveys were manually cross identified with data from the second GAIA data release (DR2) as coordinate based matching does not work reliable. The data are compared with the results of previous distance scales and to the results of a recent similar study, which was using the first data release GAIA DR1. 

Results: While the few available previous ground based and HST trigonometric parallaxes match perfectly to the new data sets, older statistical distance scales, reaching larger distances, do show small systematic differences. Restricting to those central stars, were photometric colors of GAIA show a negligible contamination by the surrounding nebula, the difference is negligible for radio flux based statistical distances, while those derived from H-alpha surface brightness still show minor differences. The DR2 study significantly improves the previous recalibration of the statistical distance scales using DR1/TGAS.

My Comment: Had not really though about it much before, but planetary nebula being big ol' clouds of gas are really tricky to measure distances to, if one is lucky you can find an embedded point-source that isn't suffering observationally from the surrounding gas. GAIA DR2, which is redefining our knowledge of our galaxy right now actually gives negative(!) parallaxes for many of these objects because space is hard.

My Scrawling Notes: (color and thumb avoidance fail today!)

The first polluted white dwarf from Gaia DR2: the cool DAZ GaiaJ1738−0826; arXiv:1806.09056

Paper: The first polluted white dwarf from Gaia DR2: the cool DAZ GaiaJ1738−0826
Authors: Carl Melis, B. Zuckerman, P. Dufour, I. Song, B. Klein
Abstract: We present the first metal-polluted single white dwarf star identified through Gaia DR2. GaiaJ1738-0826, selected from color and absolute magnitude cuts in the Gaia DR2 data, was discovered to have strong Ca~II absorption in initial spectroscopic characterization at Lick Observatory. Notably, GaiaJ1738-0826 resembles in many ways the first confirmed metal-polluted hydrogen atmosphere white dwarf, the DAZ G74-7.

My Comment: Really short article - mainly just an observation confirmation, but it makes use of GAIA DR2 to identify a candidate "weird" object, and then confirms what it is with follow-up observations, in this case spectra. I love this stuff, and wanted to grab a short GAIA DR2 paper to get started thinking about science that can be done with the data. Hint: it is a lot. Very a lot.

My Scrawling Notes: