The Radial Velocity Experiment (RAVE): Fifth Data Release (1609.03210v3)

Abstract: Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is the fifth data release from a magnitude-limited (9< I < 12) survey of stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra ($R\sim7500$) covering the Ca-triplet region (8410-8795\AA) span the complete time frame from the start of RAVE observations in 2003 to their completion in 2013. Radial velocities from 520,781 spectra of 457,588 unique stars are presented, of which 255,922 stellar observations have parallaxes and proper motions from the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. For our main DR5 catalog, stellar parameters (effective temperature, surface gravity, and overall metallicity) are computed using the RAVE DR4 stellar pipeline, but calibrated using recent K2 Campaign 1 seismic gravities and Gaia benchmark stars, as well as results obtained from high-resolution studies. Also included are temperatures from the Infrared Flux Method, and we provide a catalogue of red giant stars in the dereddened color $(J-Ks)_0$ interval (0.50,0.85) for which the gravities were calibrated based only on seismology. Further data products for sub-samples of the RAVE stars include individual abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni, and distances found using isochrones. Each RAVE spectrum is complemented by an error spectrum, which has been used to determine uncertainties on the parameters. The data can be accessed via the RAVE Web site or the Vizier database.

• The paper presents the final RAVE data release with 520,781 spectra and enhanced error spectra that significantly refine radial velocity and stellar parameter measurements.
• It recalibrates key stellar parameters using Gaia benchmarks and K2 seismic data, achieving over 15% improvement in accuracy compared to previous releases.
• DR5 complements Gaia astrometry by providing comprehensive kinematic data essential for constructing precise Galactic models and advancing stellar population studies.

Overview of "The Radial Velocity Experiment (RAVE): Fifth Data Release"

The paper presents the fifth data release (DR5) of the Radial Velocity Experiment (RAVE), a comprehensive survey targeting stars in the southern hemisphere to ascertain their radial velocities and provide insights into stellar kinematics and Galactic structure. This release integrates observations and data refinements extending from 2003 to the survey's completion in 2013, encapsulating a substantial dataset comprised of 520,781 spectra from 457,588 unique stars, each with detailed stellar parameters and various auxiliary data.

Main Contributions and Data Enhancements

DR5 achieves significant advancements over its predecessors by enhancing data accuracy and completeness. This iteration includes the final tranche of RAVE observations, recovered data from discarded observations in previous years, and a novel inclusion of error spectra, crucial for accurately assessing uncertainties on radial velocity and stellar parameters. The recalibration of stellar parameters including effective temperature, surface gravity, and metallicity further improves the accuracy of stellar characteristics, using a variety of reference points such as Gaia benchmark stars and K2 Campaign 1 seismic data.

Data Products and Methodologies

1. Spectral Data and Radial Velocities: The survey utilized medium-resolution spectra covering the Ca-triplet region, providing robust radial velocities, essential for deducing stellar motions and dynamics. The introduction of error spectra enhances the reliability of these measurements, notably for stars with low signal-to-noise ratios (SNR) or those exhibiting high temperatures.
2. Stellar Parameters: DR5 calibrates parameters using updated reference materials and external validations, yielding improved estimations—particularly for metallicity in super-solar ranges and surface gravity for giant stars. The adherence to stellar physics in deriving these parameters ensures a physical coherence across the database.
3. Elemental Abundances and Distances: Individual abundances for elements such as Mg, Al, Si, Ca, Ti, Fe, and Ni are supplied for a substantial subset of the data, leveraging an equivalent width library suited to the spectral characteristics of RAVE stars. The Bayesian methodology applied in computing distances incorporates recent advancements and expanded metallicity grids, yielding more refined distance estimates.
4. Complementing Gaia Astrometry: RAVE DR5 notably complements Gaia DR1, providing parallaxes and proper motions from the Tycho-Gaia Astrometric Solution (TGAS). This synergy enables an unprecedented level of accuracy in deriving the Galactic spatial structure and dynamics for numerous stars.

Numerical Insights and Analytical Depth

• The recalibration processes have led to superior fidelity across various stellar parameters, improved by more than 15% in some cases.
• RAVE's radial velocity measurements attain typical accuracies better than 2 km/s, with SNR exceeding 40 for many data points, confirming the survey's reliability in capturing stellar motion dynamics.

Implications and Future Work

The methodological advancements and expanded dataset underscore RAVE DR5's critical role in refining our understanding of the Milky Way's structural and dynamical properties. The data serves as a substantial counterpart to astrometric missions, providing the kinematic information necessary for constructing comprehensive Galactic models.

The integration with Gaia's astrometric capabilities heralds an era of high-precision Galactic cartography, facilitating analyses of intermediate- and large-scale Galactic features and dynamics. The paper anticipates future developments in this collaborative domain, hinting at further exploitation of Gaia's astrometric precision in tandem with RAVE’s extensive spectroscopic catalogue, which promises detailed inquiries into Galactic archaeology and stellar population studies.

In summary, RAVE DR5 sets a foundational framework for continued exploration of the Milky Way, providing a dataset with enhanced accuracy and potential for extensive ancillary use alongside Gaia data. This symbiotic relationship between spectroscopic and astrometric surveys is pivotal for advancing our comprehensive understanding of Galactic evolution.