Handling photometry

Quality cuts

In MADYS, particular attention is devoted to ensuring that only reliable photometric measurements are retained in the final database used for parameter determination. By default, SampleObject ’s mode 1 collects photometric measurements from Gaia DR2/DR3 (G, GBP, GRP) and 2MASS (J, H, Ks). Gaia DR3 G magnitudes are corrected by adopting the prescriptions by Riello et al. (2021). As regards GBP and GRP, intrinsically much more sensitive than G to contamination from nearby sources or from the background, Gaia’s phot_bp_rp_excess_factor C is used as a proxy to evaluate the quality of photometric measurements. In particular, following Riello et al. (2021), we defined a color-independent corrected BP-RP excess factor C∗ for both Gaia DR2 and Gaia DR3 and excluded GBP and GRP magnitudes with a corrected excess factor larger, in absolute value, than 3 times the standard deviation of well-behaved sources of comparable magnitude (see our paper for details).

For 2MASS and AllWISE, only sources with photometric flag ph_qual == 'A' are kept. If needed, a different value for the worst quality flag still considered reliable can be selected via the dedicated keywords max_tmass_q and max_wise_q. From the documentation:

* ``max_tmass_q`` (1): worst 2MASS photometric flag still considered reliable. Possible values, ordered by decreasing quality: 'A', 'B', 'C', 'D', 'E', 'F', 'U', 'X'. For a given choice, excludes all measurements with a lower quality flag. Default: 'A'.
* ``max_wise_q`` (1): worst ALLWISE photometric flag still considered reliable. Possible values, ordered by decreasing quality: 'A', 'B', 'C', 'U', 'Z', 'X'. For a given choice, excludes all measurements with a lower quality flag. Default: 'A'.

All information related to photometric quality can be retrieved from a SampleObject attribute named quality_table.