Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3 π Survey

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe present a catalog of 9888 M, L and T dwarfs detected in the Pan-STARRS13π Survey (PS1), covering threequarters of the sky. Our catalog contains nearly all known objects of spectral types L0-T2 in the PS1 field, with objects as early as M0 and as late as T9, and includes PS1, 2MASS, AllWISE, and GaiaDR1 photometry. We analyze the different types of photometry reported by PS1 and use two types in our catalog in order to maximize both depth and accuracy. Using parallaxes from the literature, we construct empirical SEDs for field ultracool dwarfs spanning 0.5-12 μm. We determine typical colors of M0-T9 dwarfs and highlight the distinctive colors of subdwarfs and young objects. We combine astrometry from PS1, 2MASS, and GaiaDR1 to calculate new proper motions for our catalog. We achieve a median precision of 2.9mas yr −1 , a factor of ≈3−10 improvement over previous large catalogs. Our catalog contains proper motions for 2405M6-T9 dwarfs and includes the largest set of homogeneous proper motions for L and T dwarfs published to date, 406objects for which there were no previous measurements, and 1176objects for which we improve upon previous literature values. We analyze the kinematics of ultracool dwarfs in our catalog and find evidence that bluer but otherwise generic late-M and Lfield dwarfs (i.e., not subdwarfs) tend to have tangential velocities higher than those of typical field objects. With the public release of the PS1 data, this survey will continue to be an essential tool for characterizing the ultracool dwarf population.

A new bright z = 6.82 quasar discovered with VISTA: VHS J0411–0907

“…For the MLT spectral type dwarf model, we used a new large sample of about 10,000 spectroscopically confirmed MLT brown dwarfs from Best et al (2018), which have been detected in PS1. The sample of MLT dwarfs are divided in 30 spectral types from M0 to T9.…”

“…After selecting the best-fit quasar model and the bestfit brown dwarf model for each candidates, we have selected the most likely high-z quasar candidates based on the photometric redshift and the reduced-χ 2 of the fit. The best discriminant values on the quasar and brown dwarf reducedχ 2 was empirically derived by fitting the known PS1 and DES high-z quasars (at redshift above 6) from the literature and the Best et al (2018) MLT dwarfs with our SED templates (see Eq 7,8,9). We also included in our analysis the two ULAS quasars at z > 7 using for the optical bands the DECaLS (forced photometry) magnitudes which uses the DECam camera which is the same as for the DES survey.…”

“…We used relaxed thresholds in the case where only one NIR band is available as with less data points the SED fitting is less well constrained. It is for the same reason that we used also forced photometry on the optical bands (for both the known z > 6 literature quasars and the Best et al (2018) MLT dwarfs) when there was a non-detection in some bands, to improved the fit. After this stage there are ∼4700 candidates remaining.…”

“…We used a sample of spectroscopically confirmed brown dwarfs (Best et al 2018) to create our brown dwarf templates needed for the SED fitting. To do this we fit different polynomials of order 2 to 6 on the colours (see section 3.4.2).…”

“…Results of SED fitting reduced-χ 2 for theBest et al (2018) spectroscopically confirmed MLT dwarfs (red dots) and the known z > 6 DES, PS1 and the two quasars ULAS z > 7 (blue symbols) The quasars with only the J-band available in the NIR are shown by dark blue squares. Our newly discovered quasar VHS J0411-0907 (see Section 4) is shown with a magenta star, as well as our new two BD (yellow triangles, see Section 5) and theMazzucchelli et al (2017) quasars (black points).…”