Assessing distances and consistency of kinematics in Gaia/TGAS

Michael Aumer; Ralph Sch\"onrich

RECORD

Assessing distances and consistency of kinematics in Gaia/TGAS

Ralph Schönrich, Michael Aumer

Astrophysics of Galaxies · Submitted 5 Apr 2017

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim We demonstrate that neglecting the SSFs causes severe distance biases.

how it is stated · asserted 1.00 read the record →

Comment (0) Read on arXiv ↗

Cite ▾

Claim paper

The compiled record

The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Open the compiled record

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 9,604 input tokens.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.72 · human participants 0.02 · controlled comparison 0.22 · randomized assignment 0.02 · states quantitative result 0.99 · compares with prior results 0.73 · mentions code or data availability 0.03.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; show every role.

We apply the statistical methods by Schoenrich, Binney & Asplund to assess the quality of distances and kinematics in the RAVE-TGAS and LAMOST-TGAS samples of Solar neighbourhood stars. These methods yield a nominal distance accuracy of 1-2%. Other than common tests on parallax accuracy, they directly test distance estimations including the effects of distance priors. We show how to construct these priors including the survey selection functions (SSFs) directly from the data. We demonstrate that neglecting the SSFs causes severe distance biases. Due to the decline of the SSFs in distance, the simple 1/parallax estimate only mildly underestimates distances. We test the accuracy of measured line-of-sight velocities (v_los) by binning the samples in the nominal v_los uncertainties. We find: a) the LAMOST v_los have a ~ -5 km/s offset; b) the average LAMOST measurement error for v_los is ~7 km/s, significantly smaller than, and nearly uncorrelated with the nominal LAMOST estimates. The RAVE sample shows either a moderate distance underestimate, or an unaccounted source of v_los dispersion (e_v) from measurement errors and binary stars. For a subsample of suspected binary stars in RAVE, our methods indicate significant distance underestimates. Separating a sample in metallicity or kinematics to select thick-disc/halo stars, discriminates between distance bias and e_v. For LAMOST, this separation yields consistency with pure v_los measurement errors. We find an anomaly near longitude l~(300+/-60)deg and distance s~(0.32+/-0.03)kpc on both sides of the galactic plane, which could be explained by either a localised distance error or a breathing mode.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We apply the statistical methods by Schoenrich, Binney & Asplund to assess the quality of distances and kinematics in the RAVE-TGAS and LAMOST-TGAS samples of Solar neighbourhood stars.	contribution 0.80	0.91	0.06	asserted 0.96
s1	These methods yield a nominal distance accuracy of 1-2%.	result 0.76	0.42	0.10	asserted 0.99
s2	Other than common tests on parallax accuracy, they directly test distance estimations including the effects of distance priors.	method 0.55	0.28	0.06	asserted 1.00
s3	We show how to construct these priors including the survey selection functions (SSFs) directly from the data.	method 0.83	0.91	0.05	asserted 0.99
s4	We demonstrate that neglecting the SSFs causes severe distance biases.	result 0.98	0.91	0.17	asserted 1.00
s5	Due to the decline of the SSFs in distance, the simple 1/parallax estimate only mildly underestimates distances.	result 0.89	0.82	0.07	asserted 1.00
s6	We test the accuracy of measured line-of-sight velocities (v_los) by binning the samples in the nominal v_los uncertainties.	method 0.98	0.92	0.04	asserted 0.87
s7	We find: a) the LAMOST v_los have a ~ -5 km/s offset; b) the average LAMOST measurement error for v_los is ~7 km/s, significantly smaller than, and nearly uncorrelated with the nominal LAMOST estimates.	result 1.00	0.97	0.15	asserted 1.00
s8	The RAVE sample shows either a moderate distance underestimate, or an unaccounted source of v_los dispersion (e_v) from measurement errors and binary stars.	result 0.94	0.90	0.15	hedged possibility 0.80
s9	For a subsample of suspected binary stars in RAVE, our methods indicate significant distance underestimates.	result 1.00	0.96	0.06	hedged possibility 0.76
s10	Separating a sample in metallicity or kinematics to select thick-disc/halo stars, discriminates between distance bias and e_v.	method 0.70	0.84	0.11	asserted 0.97
s11	For LAMOST, this separation yields consistency with pure v_los measurement errors.	result 0.94	0.95	0.08	hedged possibility 0.63
s12	We find an anomaly near longitude l~(300+/-60)deg and distance s~(0.32+/-0.03)kpc on both sides of the galactic plane, which could be explained by either a localised distance error or a breathing mode.	result 0.91	0.93	0.08	hedged possibility 0.89

What kind of paper the classifier reports this is: empirical study 0.66 · evidence from analysis of existing data 1.00.

What was examined, and what was not

sources read

arXiv listing abstract v2

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper

Original abstract

We apply the statistical methods by Schoenrich, Binney & Asplund to assess the quality of distances and kinematics in the RAVE-TGAS and LAMOST-TGAS samples of Solar neighbourhood stars. These methods yield a nominal distance accuracy of 1-2%. Other than common tests on parallax accuracy, they directly test distance estimations including the effects of distance priors. We show how to construct these priors including the survey selection functions (SSFs) directly from the data. We demonstrate that neglecting the SSFs causes severe distance biases. Due to the decline of the SSFs in distance, the simple 1/parallax estimate only mildly underestimates distances. We test the accuracy of measured line-of-sight velocities (v_los) by binning the samples in the nominal v_los uncertainties. We find: a) the LAMOST v_los have a ~ -5 km/s offset; b) the average LAMOST measurement error for v_los is ~7 km/s, significantly smaller than, and nearly uncorrelated with the nominal LAMOST estimates. The RAVE sample shows either a moderate distance underestimate, or an unaccounted source of v_los dispersion (e_v) from measurement errors and binary stars. For a subsample of suspected binary stars in RAVE, our methods indicate significant distance underestimates. Separating a sample in metallicity or kinematics to select thick-disc/halo stars, discriminates between distance bias and e_v. For LAMOST, this separation yields consistency with pure v_los measurement errors. We find an anomaly near longitude l~(300+/-60)deg and distance s~(0.32+/-0.03)kpc on both sides of the galactic plane, which could be explained by either a localised distance error or a breathing mode.

Human review

How Pith checks papers → · Full audit of this paper →

References

How the literature uses it

5 arXiv papers cite this in 13 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 7 sentences without a confident label

Uses its method or tool 1 paper

To correct for this it is necessary to adopt a prior based on estimated density distributions, as in [ref] , or on density and velocity distributions as in [ref] .

The Lives of Stars: Insights From the TGAS-RAVE-LAMOST Dataset · Data · 0.80

Uses its data or values 3 papers

As noted earlier, we also replace the LAMOST pipeline velocity errors with a uniform error of 7.2 km s$^-1$, which is the standard error found in [ref] .

The Lives of Stars: Insights From the TGAS-RAVE-LAMOST Dataset · Velocity · 1.00
These values are adopted from [ref] .

The Flattening Metallicity Gradient in the Milky Way's Thin Disk · Orbits and Coordinates · 1.00
These positions and velocities are all adopted from [ref] .

A LAMOST BHB Catalog and Kinematics Therein I: Catalog and Halo Properties · Coordinates and Velocities · 0.97

Cites it as support 1 paper

At the accuracy required for our comparison, this is a reasonable assumption as was shown by [ref] .

Migration and kinematics in growing disc galaxies with thin and thick discs · RAVE-TGAS data · 0.99

What it cites · 7 sentences without a confident label

Uses data or values from 1 paper

For this work, we crossmatch TGAS data from Gaia DR1 [ref] both with RAVE DR5 [ref] and with DR2 of LAMOST [ref] .

The Radial Velocity Experiment (RAVE): Fifth Data Release · TGAS data · 1.00

Cites as support 1 paper

This conclusion would be supported by [ref] , who report a problem possibly coinciding with the Gaia scanning regime change at a similar position on the sky (cf. their Fig. 28).

Gaia Data Release 1: Catalogue validation · A bump in the distance statistics · 0.97

Cites as background 3 papers

Since the first release of Tycho-Gaia Astrometric Solution (TGAS) data [ref] there has been a variety of papers examining the quality of the data, ranging from the original validation paper [ref] to studies with standard candles, like red giants and red giant clump stars [ref] .

Asteroseismic versus Gaia distances: a first comparison · Introduction · 0.98
Since the first release of Tycho-Gaia Astrometric Solution (TGAS) data [ref] there has been a variety of papers examining the quality of the data, ranging from the original validation paper [ref] to studies with standard candles, like red giants and red giant clump stars [ref] .

Using red clump stars to correct the Gaia DR1 parallaxes · Introduction · 0.98
A thorough compilation of standard validations of TGAS astrometry is found in [ref] .

Gaia Data Release 1: Catalogue validation · Introduction · 0.95

Discussion

Know something about this paper? Leave a comment, or highlight any passage above to comment on it.