Stellar properties of objects in the SDF (Richmond, 2005) ================================================================================ Properties of stars in the Subaru Deep Field Richmond, M. W. < > = ================================================================================ ADC_Keywords: Combined data ; Galactic pole, north ; Stars, faint Keywords: stars: statistics -- methods: data analysis Abstract: We investigate the properties of objects in the Subaru Deep Field (SDF), using public catalogs constructed from images in several optical passbands. Using a small subset of objects most likely to be stars, we construct a stellar locus in three-dimensional color space. We then compare the position of all objects relative to this locus to create larger samples of stars in the SDF with rough spectral types. The number counts of stars defined in this way are consistent with those of current models of the Galaxy. Description: Using photometry and other parameters provided in the SDF catalogs (Kashikawa et al. 2004), we have constructed a stellar locus in three-dimensional space. We assign each object two scores: a morphological one, based on its shape, and a color one, based on its proximity to the stellar locus in color space. We have calibrated how position along the stellar locus corresponds to spectral type, so that we can assign a rough spectral type to every object (which will be meaningful only for objects actually near the stellar locus). We include information for all objects in the SDF Rc-based catalogs, even those which are obviously not stars (because they are clearly extended and/or far from the stellar locus), so that the user can choose the exact cutoff between stars and galaxies, or create a catalog of non-stellar objects in the SDF. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file sdflocus.dat 160 189380 Measured and derived properties of all qualifying objects in the SDF Rc-based catalog -------------------------------------------------------------------------------- Byte-by-byte Description of file: sdflocus.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 I6 --- Index Index in Kashikawa et al. Rc-based catalogs 9- 17 F9.5 deg RA Right ascension (J2000.0) 19- 27 F9.5 deg Dec Declination (J2000.0) 29- 35 F7.4 mag Bmag Magnitude in Johnson B passband 37- 43 F7.4 mag Vmag Magnitude in Johnson V passband 45- 51 F7.4 mag Rcmag Magnitude in Cousins Rc passband 53- 59 F7.4 mag ipmag Magnitude in Suprime-Cam i-prime passband 61- 67 F7.4 mag zpmag Magnitude in Suprime-Cam z-prime passband 69- 72 F4.2 --- B_cls "class_star" value in B image (1) 74- 77 F4.2 --- V_cls "class_star" value in V image (1) 79- 82 F4.2 --- Rc_cls "class_star" value in Rc image (1) 84- 87 F4.2 --- ip_cls "class_star" value in i-prime image (1) 89- 92 F4.2 --- zp_cls "class_star" value in z-prime image (1) 94- 99 F6.3 mag B_delta difference of aperture magnitudes in B (2) 101-106 F6.3 mag V_delta difference of aperture magnitudes in V (2) 108-113 F6.3 mag Rc_delta difference of aperture magnitudes in Rc (2) 115-120 F6.3 mag ip_delta difference of aperture magnitudes in i-prime (2) 122-127 F6.3 mag zp_delta difference of aperture magnitudes in z-prime (2) 129-130 I2 --- m_score overall morphological score (3) 132-136 F5.2 mag milestone distance from end of stellar locus (4) 138-141 F4.2 --- c_score color score (5) 143 A1 --- spectype spectral type, based on milestone 145-146 I2 --- locus index of locus point closest to object 148-153 F6.3 mag ldist distance from object to stellar locus, measured along major axis of locus 155-160 F6.3 mag mdist distance from object to stellar locus, measured along minor axis of locus -------------------------------------------------------------------------------- Note (1): The "class_star" value is a measure of how star-like an object appears, based on SExtractor output. We copy this value directly from the SDF public catalogs of Kashikawa et al. (2004). The value ranges from 0.0 (very extended) to 1.0 (very star-like). Note (2): The "delta" value is the difference between the magnitude measured in an aperture of radius 2 arcseconds and the magnitude measured in an aperture of radius 3 arcseconds. We find that values in the range 0.10 < delta < 0.18 are consistent with point-like objects. Note (3): For each of the 5 passbands, we make 2 tests based on the shape of an object: we ask if its "class_star" value is > 0.90, and if its "delta" value is in the range 0.10 - 0.18. Each test passed counts as 1. This score is the sum of all tests: it ranges from 0 (not star-like) to 10 (very star-like). Note (4): We first find the closest approach of the stellar locus to the colors of each object, then measure the distance along the locus to that closest approach. Distance of zero corresponds approximately to spectral class F0. Note (5): A measure of the degree to which the colors of this object (including their uncertainties) fall within the stellar locus at the point of closest approach. Values range from 0.0 (color is completely outside the stellar locus) to 1.0 (color is completely within the locus). -------------------------------------------------------------------------------- Acknowledgements: References: Kashikawa et al., 2004PASJ...56.1011K The Subaru Deep Field: The Optical Imaging Data ================================================================================ (End) Michael Richmond [RIT, USA] 21-Aug-2005