J/ApJS/183/261 Optical photometry of the ONC (Da Rio+, 2009) ================================================================================ A multi-color optical survey of the Orion nebula cluster. I. The catalog. Da Rio N., Robberto M., Soderblom D.R., Panagia N., Hillenbrand L.A., Palla F., Stassun K. =2009ApJS..183..261D ================================================================================ ADC_Keywords: Photometry, H-alpha ; Photometry, UBVRI ; Equivalent widths ; Stars, M-type ; Surveys ; Spectral types Keywords: catalogs - stars: formation - stars: pre-main sequence - open clusters and associations: individual (Orion Nebula Cluster) - stars: luminosity function, mass function Abstract: We present U, B, V, I broadband, 6200{AA} TiO medium band, and H{alpha} narrow band photometry of the Orion Nebula Cluster (ONC) obtained with the WFI imager at the ESO/MPI 2.2 telescope at La Silla Observatory. The nearly simultaneous observations cover the entire ONC in a field of about 34x34arcmin^2^. They enable us to determine stellar colors avoiding the additional scatter in the photometry induced by stellar variability typical of pre-main-sequence stars. We identify 2612 point-like sources in the I band; 58%, 43%, and 17% of them are also detected in V, B, and U, respectively. 1040 sources are identified in the H{alpha} band. In this paper we present the observations, the calibration techniques adopted, and the resulting catalog. We show the derived color-magnitude diagram of the population and discuss the completeness of our photometry. We define a spectrophotometric TiO index that takes into account the fluxes in the V, I, and TiO bands. Comparing it with spectral types of ONC members in the literature, we find a correlation between the index and the spectral type valid for M-type stars, which is accurate to better than 1 spectral subclass for M3-M6 types and better than 2 spectral subclasses for M0-M2 types. This allows us to newly classify 217 stars. Description: The Wide Field Imager (WFI) is a focal reducer-type camera mounted at the Cassegrain focus of the 2.2-m MPG/ESO telescope at La Silla. Our target field was observed in service observing mode on the nights of 2005 January 1 and 2 (hereafter indicated as Night A and Night B, respectively). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 110 2621 WFI photometric catalog relative to Night A observations table4.dat 48 217 New M-type stars classified from the [TiO] index table5.dat 94 1040 H{alpha} excess -------------------------------------------------------------------------------- See also: J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997) J/AJ/121/1676 : ONC low-mass stars photometry (Rebull+, 2001) J/ApJ/574/258 : Orion nebula X-ray-emitting young stars (Feigelson+, 2002) J/ApJS/160/353 : Membership of the Orion nebula population (Getman+, 2005) J/ApJ/660/704 : Optical and X-ray variability of ONC PMS (Stassun+, 2007) J/ApJ/660/1462 : Abundances of ONC X-ray PMS stars (Maggio+, 2007) J/A+A/502/883 : I phot. of very low mass ONC stars (Rodriguez-Ledesma+, 2009) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- [DRS2009] Identification number 6- 7 I2 h RAh Hour of Right Ascension (J2000) 9- 10 I2 min RAm Minute of Right Ascension (J2000) 12- 16 F5.2 s RAs Second of Right Ascension (J2000) 18 A1 --- DE- Sign of the Declination (J2000) 19- 20 I2 deg DEd Degree of Declination (J2000) 22- 23 I2 arcmin DEm Arcminute of Declination (J2000) 25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000) 30- 37 F8.5 mag Umag ? U band Vega magnitude (1) 39- 44 F6.4 mag e_Umag ? Error in Umag 46- 53 F8.5 mag Bmag ? B band Vega magnitude (1) 55- 60 F6.4 mag e_Bmag ? Error in Bmag 62- 69 F8.5 mag Vmag ? V band Vega magnitude (1) 71- 76 F6.4 mag e_Vmag ? Error in Vmag 78- 85 F8.5 mag TiO ? TiO band Vega magnitude (1) 87- 92 F6.4 mag e_TiO ? Error in TiO 94- 99 F6.3 mag Imag I band Vega magnitude (1) 101-105 F5.3 mag e_Imag Error in Imag 107-110 I4 --- [H97b] ? Hillenbrand 1997 (Cat. J/AJ/113/1733) catalog identification -------------------------------------------------------------------------------- Note (1): the filters have central wavelength and width ({AA}): ------------------- Name lamc FWHM ------------------- U 3404 732 B 4511 1335 V 5395 893 I 8269 2030 TiO 6208 194 Ha 6588 74 ------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- Seq Running number 5- 8 I4 --- [DRS2009] Identification number from table2.dat 10- 11 I2 h RAh hour of right ascension (J2000) 13- 14 I2 min RAm Minute of right ascension (J2000) 16- 20 F5.2 s RAs Second of right ascension (J2000) 22 A1 --- DE- Sign of declination (J2000) 23- 24 I2 deg DEd Degree of declination (J2000) 26- 27 I2 arcmin DEm Arcminute of declination (J2000) 29- 32 F4.1 arcsec DEs Arcsecond of declination (J2000) 34- 39 F6.3 mag [TiO] Index of [TiO] (2) 41- 44 A4 --- SpT Spectral type 46- 48 F3.1 --- e_SpT Uncertainty of spectral type -------------------------------------------------------------------------------- Note (2): the [TiO] index is defined as the difference between the linear interpolation at 620nm of the V and I magnitudes and the apparent magnitude in the TiO band: [TiO] = (V - (V-I).f) - m(TiO) where f = 813/2874 = 0.283 is the ratio ({lambda}_TiO_-{lambda}_V_)/({lambda}_I_-{lambda}_V_) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Seq Running identification number 6- 9 I4 --- [DRS2009] Identification number from table2.dat 11- 12 I2 h RAh Hour of Right Ascension (J2000) 14- 15 I2 min RAm Minute of Right Ascension (J2000) 17- 21 F5.2 s RAs Second of Right Ascension (J2000) 23 A1 --- DE- Sign of the Declination (J2000) 24- 25 I2 deg DEd Degree of Declination (J2000) 27- 28 I2 arcmin DEm Arcminute of Declination (J2000) 30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000) 35- 43 E9.2 0.1nm EWA H{alpha} equivalent width in Angstroms (1) 45- 54 E10.2 Hz EWHz H{alpha} equivalent width in Hertz (1) 56- 65 E10.2 mW/m2 Ex.erg H{alpha} excess in erg/s/cm^2^ 67- 75 E9.2 mJy Ex.mJy H{alpha} excess in mJy 77- 85 E9.2 mW/m2 Cont.erg H{alpha} continuum in erg/s/cm^2^ 87- 94 F8.4 mJy Cont.mJy H{alpha} continuum in mJy -------------------------------------------------------------------------------- Note (1): We follow the standard convention, i.e. positive E.W. is associated with an absorption, negative E.W. with an emission. -------------------------------------------------------------------------------- History: From electronic version of the journal References: Da Rio et al. Paper II. 2010ApJ...722.1092D Cat. J/ApJ/722/1092 ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 19-Jan-2010