Building an Acceleration Ladder with Tidal Streams and Pulsar Timing

TL;DR

This paper combines stellar stream analysis and pulsar timing to constrain the Milky Way's gravitational potential, creating an 'acceleration ladder' that integrates direct and indirect acceleration measurements for improved galactic modeling.

Contribution

It introduces a joint analysis method using stellar streams and pulsar accelerations to better constrain the Milky Way's potential, forming an 'acceleration ladder' for enhanced galactic studies.

Findings

Preferred potential model is a two-component Staeckel potential.

Streams suggest a lower Oort limit than pulsar timing.

Calibration method to correct stream-based acceleration estimates.

Abstract

We analyze stellar streams in action-angle coordinates combined with recent local direct acceleration measurements to provide joint constraints on the potential of our Galaxy. Our stream analysis uses the Kullback-Leibler divergence with a likelihood analysis based on the two-point correlation function. We provide joint constraints from pulsar accelerations and stellar streams for local and global parameters that describe the potential of the Milky Way (MW). Our goal is to build an ``acceleration ladder", where direct acceleration measurements that are currently limited in dynamic range are combined with indirect techniques that can access a much larger volume of the MW. To constrain the MW potential with stellar streams, we consider the Palomar 5, Orphan, Nyx, Helmi and GD1 streams. Of the potential models that we have considered here, the preferred potential for the streams is a two-component Staeckel potential. We also compare the vertical accelerations from stellar streams and pulsar timing, defining a function $f(z) = \alpha_{1pulsar}z - \frac{\partial\Phi}{\partial z}$, where $\Phi$ is the MW potential determined from stellar streams, and $\alpha_{1~\rm pulsar}z$ is the vertical acceleration determined from pulsar timing observations. Our analysis indicates that the Oort limit determined from streams is consistently (regardless of the choice of potential) lower than that determined from pulsar timing observations. The calibration we have derived here may be used to correct the estimate of the acceleration from stellar streams.