=============================================================================================================== ReadMe =============================================================================================================== List of files in CSV directory: parameters_MARCS_LIBRARY.csv parameters_PHOENIX_LIBRARY.csv parameters_A_LIBRARY.csv parameters_OB_LIBRARY.csv =============================================================================================================== This ReadMe describes the 4 files that contain the full set of parameters accompanying the spectral simulations made for CU8. Each file is named according to their spectral library used as input for simulations. Each line of the files gives, for a star with the specified physical parameters, the derived magnitudes, extinctions and color excesses based on a specific simulated spectra. See the table at the end of this Readme for a detailed description of each column. We produced these simulations at a fixed apparent G magnitude of 15 mag (GG) and we provide the corresponding GBP and GRP for each source. Simulations of BP/RP spectra are needed to develop/prepare some CU8 Apsis modules. A simulator developed in DPAC by CU5 takes as input a higher resolution, not-normalized spectra. CU8 collected a series of spectral libraries for this purpose, and in DR3 Apsis used these four libraries: MARCS, PHOENIX, A, OB. Full details on simulations and spectral libraries are given in Section 11.2.3 of the Gaia DR3 A synthetic spectrum is defined by its effective temperature (teff), surface gravity (logg), and metallicity [M/H]. We provide [Fe/H] (feH) and [alpha/Fe] (alphaFe), and [M/H] = [Fe/H] + [alpha/Fe]. The spectral libraries available to CU8 are computed at discrete values of teff, logg, feH. alphaFe is fixed to the solar values (=0.0) for all but the MARCS library, which allows [alpha/Fe] to vary with [Fe/H]. See the documentation for more details on metallicity (Section 11.2.3). A synthetic spectrum is normalized to a stellar unit surface, we thus need at least the radius (R) to obtain the absolute flux. This information is provided by evolutionary models. We developed a specific procedure for matching a spectrum with isochrones. A flag (parameter 17) tags if the match is satisfactory (=0) or not (=1). See Section 11.2.3 of the Gaia DR3 online documentation for details. Once the radius of the star is known, we can scale the synthetic spectrum to simulate the absolute flux of the star (at 10 pc), and using the eDR3 passbands we can derive the absolute magnitude MG. Given MG, the extinction in the G band AG and the apparent magnitude GG, we can derive the distance (d) of the star. These quantities are needed by GSPPhot. The emission from a star can be attenuated by interstellar absorption. To simulate extinction, we use the Fitzpatrick (1999) extinction curve. We simulated each synthetic spectrum at different levels of extinction, parametrized by A0 values (monochromatic extinction at 541.4 nm). Details are provided in Section 11.2.3 of the online documentation. From these simulations, we computed the photometry and extinction measurements in different passbands. Those were used by different steps in the preparation of Apsis and in the validation of its results. We emphasize that we computed the extinction measurements by integrating the reddened spectra, i.e. we did not use any approximation or calibration. The extinction in a given passband comes from the difference between the reddened magnitude and the un-reddened one. ==== =========== ================= ============================ ======================================== ====================================== # Name Unit UCD Description notes ==== =========== ================= ============================ ======================================== ===================================== 1 runID meta.code running Gaia ID unique Gaia-like ID 2 GG mag phot.mag;em.opt Gaia G magnitude normalized to G=15mag 3 GBP mag phot.mag;em.opt.B Gaia GBP magnitude normalized to G=15mag 4 GRP mag phot.mag;em.opt.R Gaia GBP magnitude normalized to G=15mag 5 A0 mag phys.absorption;em.opt; extinction parameter monochromatic extinction at 541.4 nm 6 AV mag phys.absorption;em.opt.V; extinction in the V band computed by spectrum integration 7 AG mag phys.absorption;em.opt.G; extinction in the G band computed by spectrum integration 8 ABP mag phys.absorption;em.opt.B; extinction in the BP band computed by spectrum integration 9 ARP mag phys.absorption;em.opt.R; extinction in the RP band computed by spectrum integration 10 Ebprp mag phys.absorption;phot.color color excess in BP-RP color computed by spectrum integration 11 Ebv mag phys.absorption;phot.color color excess in B-V color computed by spectrum integration 12 VI0 mag phot.color V-I color without reddening computed by spectrum integration 13 VIc mag phot.color V-I color with reddening computed by spectrum integration 14 Mg mag phot.mag;em.opt Absolute magnitude in the Gaia G band computed scaling the synthetic spectrum with R 15 R Rsun phys.size.radius Stellar radius from match with evolutionary models 16 d pc pos.distance Linear distance of the source computed from MG,Gg,AG 17 flag meta.code isochrone matching flag (0 or 1) 0=good match; 1=bad match 18 teff K phys.temperature.effective Stellar effective temperature 19 logg log10(cm/s**2) phys.gravity Stellar gravity 20 feH dex phys.abund.Fe Stellar [Fe/H] abundance ratio [M/H]=[Fe/H] + [alpha/Fe] 21 alphaFe dex phys.abund Stellar [alpha/Fe] abundance ratio ==== =========== ================= ============================ ======================================== ======================================