Distances for the Gaia RV set with corrected parallaxes
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The datasets are described in https://arxiv.org/abs/1902.02355 , which is submitted to MNRAS. Each file contains a distance derivation under different assumptions for the Gaia RV dataset. Please note the following: to allow for freedom in choice of cuts, we have limited ourselves to just minimal cuts: parallax/parallaxerr > 3, detected G,G_BP,G_RP magnitudes > 0 mag, vlos_err < 10 km/s, n_vis > 5, reasonably measured RV (<5550 km/s), distance and 1/parallax < 10 kpc Note that these cuts are NOT sufficient to ensure quality of the sample. We strongly advise to use the quality criteria laid out in Schoenrich, McMillan and Eyer (2019), and test for the effects of a cut in galactic latitude b > 10 degrees for most applications. The file format is .csv (comma separated) with the following columns (a key is in row 1)<br> index: running number in our sample<br> sourceid: Gaia Source ID<br> E_dist: expectation value for the distance, unit is kpc<br> distm2: second moment of distance probability distribution (use the usual formula to get the variance/dispersion)<br> distm3: third moment of distance probability distribution<br> distm4: fourth moment """"<br> parallax: The Gaia parallax _including_ the offset correction chosen, unit is mas<br> parallax/parallaxerr : ratio of parallax to parallax uncertainty. Again, both parallax and parallaxerror contain the corrections. Use this and the last column to obtain the parallax uncertainty for quality cuts<br> x: x coordinate (radial coordinate in local cartesian frame), unit is kpc<br> y: y coordinate in the azimuthal direction, unit is kpc<br> z: z coordinate (perpendicular to the plane), relative to the Sun, unit is kpc. Please add the solar offset from the plane that you favor (0.02 kpc, Joshi et al., or the Gerhard & Bland-Hawthorn review are good values)<br> R: galactocentric radius (in-plane, cylindrical coordinates), unit is kpc<br> U_g: cylindrical radial velocity in a galactocentric frame (positive taken inwards), unit is km/s<br> v_phi: azimuthal velocity (V_g, azimuthal direction), unit is km/s<br> v_z: velocity component upwards perpendicular to the plane, unit is km/s<br> vlos: line-of-sight velocity as provided in the Gaia RV datasets<br> vloserr: line-of-sight velocity error as provided in the Gaia RV datasets<br> gl: Galactic longitude l (degrees)<br> gb: Galactic latitude b (degrees)<br> pml: proper motion in l (mas/yr)<br> pmb: proper motion in b (mas/yr)<br> pml_err: proper motion error/uncertainty in l (mas/yr)<br> pmb_err: proper motion error in b (mas/yr)<br> E_bprp: BP-RP excess flux factor (provided in Gaia catalogue)<br> excessnoise: astrometric excess noise<br> Gmag: Gaia G magnitude<br> Rmag: Gaia G_RP magnitude<br> B-Rcolour: G_BP - G_RP (colour in mag)<br> nvis: number of visibility periods<br> eclat: ecliptic latitude (degrees) Each file contains a different set of assumptions that result in a near-zero average distance bias, as discussed in the paper: We recommend using either:<br> gaiaRVdelp54delsp43 : Increased parallax uncertainty by 0.043 mas in quadrature, corrected for parallax offset of 0.054 mas gaiaRVdelpeqspdelsp43 : Increased parallax uncertainty by 0.043 mas in quadrature, corrected for a parallax offset = modified parallax error For comparison and applications that need long-range in distance s, it may be interesting to use:<br> gaiaRVdelp48delsp00 : only increased parallaxes by an offset of 0.048 mas. Distance bias on average is stable out to 4kpc or more, but you have to be wary of random errors. <br> All distances were derived with the standard prior described in Schoenrich, McMillan and Eyer (2019); the parameter for the additional exponential function in the prior at very large s > 4 kpc is 0.06/kpc If you need specific subsamples of stars, we advice to draw a new prior with the method of Schoenrich & Aumer (2017) and then re-derive the distances. We are also happy to help with that and provide you with the necessary code. Please note that our definition (angular distance per time in the direction of l, b) of pml and pmb is frequently noted with a * in other derivations. Please also note that why we used z_Sun = 0.02 kpc in the underlying analysis and distance prior, the value in the catalogue is given relative to the Sun (i.e. add the Solar offset that you favour).
本数据集的详细说明见于https://arxiv.org/abs/1902.02355，该文稿已提交至MNRAS。 每份文件均包含基于不同假设针对盖亚径向速度数据集（Gaia RV）得到的距离推导结果。 请注意：为保留筛选条件的选择自由度，我们仅设置了最基础的筛选阈值：视差/视差误差>3、已探测到的G、G_BP、G_RP星等均>0星等、视向速度误差<10 km/s、可见周期数>5、径向速度测量合理（<5550 km/s），且距离与1/视差均<10 kpc。 需注意，上述筛选阈值并不足以保证样本质量。我们强烈建议采用Schoenrich、McMillan与Eyer（2019）提出的质量判据，并在多数应用中增设银道纬度b>10°的筛选条件以验证其影响。 文件格式为逗号分隔值（CSV）格式，首行为列名索引，各字段说明如下： - index：样本序号 - sourceid：盖亚源ID（Gaia Source ID） - E_dist：距离期望值，单位为千秒差距（kpc） - distm2：距离概率分布的二阶矩（可通过标准公式计算方差/离散度） - distm3：距离概率分布的三阶矩 - distm4：距离概率分布的四阶矩 - parallax：盖亚视差（包含所选偏移校正，单位为毫角秒（mas）） - parallax/parallaxerr：视差与视差误差的比值。视差及视差误差均已包含校正项，可结合本项与前一列获取视差误差以用于质量筛选 - x：局部笛卡尔坐标系下的x坐标（径向坐标），单位为kpc - y：方位角方向的y坐标，单位为kpc - z：垂直于银道面的z坐标（相对于太阳），单位为kpc。请自行加上所选的太阳相对于银道面的偏移量（推荐值为0.02 kpc，参见Joshi等人的研究或Gerhard与Bland-Hawthorn的综述） - R：银心距（柱坐标系下的平面内半径），单位为kpc - U_g：银心坐标系下的柱径向速度（正向为向内），单位为千米每秒（km/s） - v_phi：方位角速度（V_g，方位角方向），单位为km/s - v_z：垂直于银道面向上的速度分量，单位为km/s - vlos：盖亚径向速度数据集提供的视向速度 - vloserr：盖亚径向速度数据集提供的视向速度误差 - gl：银经l，单位为度（°） - gb：银纬b，单位为° - pml：银经方向的自行，单位为毫角秒每年（mas/yr） - pmb：银纬方向的自行，单位为mas/yr - pml_err：银经方向自行的误差，单位为mas/yr - pmb_err：银纬方向自行的误差，单位为mas/yr - E_bprp：BP-RP过剩流量因子（取自盖亚星表） - excessnoise：天体测量过剩噪声 - Gmag：盖亚G星等 - Rmag：盖亚G_RP星等 - B-Rcolour：G_BP - G_RP色指数，单位为星等 - nvis：可见周期数 - eclat：黄道纬度，单位为° 每份文件对应一组不同的假设，可实现平均距离偏差接近零，具体详见论文： 我们推荐使用以下两种设置： 1. gaiaRVdelp54delsp43：视差不确定性通过叠加0.043 mas的方和根误差得到修正，并针对0.054 mas的视差偏移进行了校正 2. gaiaRVdelpeqspdelsp43：视差不确定性通过叠加0.043 mas的方和根误差得到修正，并针对与修正后视差误差相等的视差偏移进行了校正 若需进行长距离范围的对比或应用，可选用：gaiaRVdelp48delsp00：仅针对0.048 mas的视差偏移进行校正。该设置下平均距离偏差在4 kpc及以上范围内保持稳定，但需警惕随机误差的影响。 所有距离推导均采用Schoenrich、McMillan与Eyer（2019）中描述的标准先验；当距离s>4 kpc时，先验中额外指数函数的参数为0.06/kpc。 若您需要特定的恒星子样本，我们建议采用Schoenrich与Aumer（2017）的方法重新构建先验并重新推导距离。我们也乐意提供协助并提供所需代码。 请注意：我们对pml与pmb的定义（沿l、b方向的单位时间角距离）在其他推导中常标注星号*。 另需注意：尽管我们在基础分析与距离先验中采用了z_Sun=0.02 kpc，但本星表中的z坐标均相对于太阳给出（即请自行加上所选的太阳偏移量）。
