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
.