DELVE-ing into the Jet: A Thin Stellar Stream on a Retrograde Orbit at 30 kpc

P S Ferguson,J D Sakowska,Kiyan Tavangar ,S E Koposov ,Yumi Choi ,B Yanny,Nora Shipp ,N Kuropatkin,Burçin Mutlu-Pakdil ,Denis Erkal ,Andrew B Pace ,Sid Mau ,Knut Olsen ,W Cerny,Guy S Stringfellow ,A Drlica-Wagner,A H Riley,Jeffrey L Carlin ,Ting Li ,C E Martı́nez-Vázquez ,D J James,J L Marshall,M Adamów

doi:10.3847/1538-3881/ac3492

Abstract

Abstract We perform a detailed photometric and astrometric analysis of stars in the Jet stream using data from the first data release of the DECam Local Volume Exploration Survey DR1 and Gaia EDR3. We discover that the stream extends over ∼ 29° on the sky (increasing the known length by 18°), which is comparable to the kinematically cold Phoenix, ATLAS, and GD-1 streams. Using blue horizontal branch stars, we resolve a distance gradient along the Jet stream of 0.2 kpc deg−1, with distances ranging from D ⊙ ∼ 27–34 kpc. We use natural splines to simultaneously fit the stream track, width, and intensity to quantitatively characterize density variations in the Jet stream, including a large gap, and identify substructure off the main track of the stream. Furthermore, we report the first measurement of the proper motion of the Jet stream and find that it is well aligned with the stream track, suggesting the stream has likely not been significantly perturbed perpendicular to the line of sight. Finally, we fit the stream with a dynamical model and find that it is on a retrograde orbit, and is well fit by a gravitational potential including the Milky Way and Large Magellanic Cloud. These results indicate the Jet stream is an excellent candidate for future studies with deeper photometry, astrometry, and spectroscopy to study the potential of the Milky Way and probe perturbations from baryonic and dark matter substructure.

Highlights

Stellar streams form through the tidal disruption of dwarf galaxies and globular clusters as they accrete onto a larger host galaxy (e.g., Newberg & Carlin 2016)
We fit the stream with a dynamical model and find that the stream is on a retrograde orbit, and is well fit by a gravitational potential including the Milky Way and Large Magellanic Cloud. These results indicate the Jet stream is an excellent candidate for future studies with deeper photometry, astrometry, and spectroscopy to study the potential of the Milky Way and probe perturbations from baryonic and dark matter substructure
Using the Dark Energy Camera (DECam) Local Volume Exploration Survey (DELVE) Data Release 1 (DR1) catalog cross-matched with Gaia EDR3 (Section 2.1), we identify candidate blue horizontal branch (BHB) stars and use them to measure a distance gradient along the Jet stream

Summary

Introduction

Stellar streams form through the tidal disruption of dwarf galaxies and globular clusters as they accrete onto a larger host galaxy (e.g., Newberg & Carlin 2016). The formation of stellar streams is an expected feature of hierarchical models of galaxy formation where large galaxies grow through mergers of smaller systems (LyndenBell & Lynden-Bell 1995; Johnston et al 2001). Due to their formation mechanism, transient nature, and dynamical fragility, stellar streams provide a direct and powerful probe of the gravitational field in galactic halos at both large and small scales (e.g., Johnston et al 1999, 2002; Ibata et al 2002). The population of cold stellar streams with small internal velocity dispersions provides a sensitive probe of the gravitational field far from the Milky Way disk

Methods

Findings

Discussion

Conclusion