Transformations between 2MASS, SDSS and BVRI photometric systems: bridging the near infrared and optical

TL;DR

This paper develops accurate color transformations between 2MASS, SDSS, and BVRI photometric systems using a carefully selected sample of stars, enabling better distance and density estimations in Galactic studies.

Contribution

It provides new, high-quality color transformations between near-infrared and optical systems, considering metallicity and population type dependencies, not previously addressed.

Findings

Transformations enable accurate distance estimations.

Sample selection criteria improve transformation reliability.

Facilitates Galactic structure modeling at various distances.

Abstract

We present colour transformations for the conversion of the {\em 2MASS} photometric system to the Johnson-Cousins $UBVRI$ system and further into the {\em SDSS} $ugriz$ system. We have taken {\em SDSS} $gri$ magnitudes of stars measured with the 2.5-m telescope from $SDSS$ Data Release 5 (DR5), and $BVRI$ and $JHK_{s}$ magnitudes from Stetson's catalogue and \citet{Cu03}, respectively. We matched thousands of stars in the three photometric systems by their coordinates and obtained a homogeneous sample of 825 stars by the following constraints, which are not used in previous transformations: 1) the data are de-reddened, 2) giants are omitted, and 3) the sample stars selected are of the highest quality. We give metallicity, population type, and transformations dependent on two colours. The transformations provide absolute magnitude and distance determinations which can be used in space density evaluations at short distances where some or all of the {\em SDSS} $ugriz$ magnitudes are saturated. The combination of these densities with those evaluated at larger distances using {\em SDSS} $ugriz$ photometry will supply accurate Galactic model parameters, particularly the local space densities for each population.