J/ApJ/706/1484 Photometry and spectroscopy in IC 2391 (Boudreault+, 2009) ================================================================================ A constraint on brown dwarf formation via ejection: radial variation of the stellar and substellar mass function of the young open cluster IC 2391. Boudreault S., Bailer-Jones C.A.L. =2009ApJ...706.1484B ================================================================================ ADC_Keywords: Clusters, open ; Photometry ; Spectroscopy ; Radial velocities ; Stars, M-type ; Stars, masses ; Effective temperatures ; Spectral types ; Equivalent widths Keywords: open clusters and associations: individual (IC 2391) - stars: low-mass, brown dwarfs - stars: luminosity function, mass function Abstract: We present the stellar and substellar mass function (MF) of the open cluster IC 2391, plus its radial dependence, and use this to put constraints on the formation mechanism of brown dwarfs (BDs). Our multi-band optical and infrared photometric survey with spectroscopic follow-up covers 11deg^2^, making it the largest survey of this cluster to date. From our preliminary spectroscopic follow-up, to confirm BD status and cluster membership, we find that all candidates are M dwarfs (in either the field or the cluster), demonstrating the efficiency of our photometric selection method in avoiding contaminants (e.g., red giants). About half of our photometric candidates for which we have spectra are spectroscopically confirmed as cluster members; two are new spectroscopically confirmed BD members of IC 2391. Description: The survey consists of 35 34'x33' fields extending to 3{deg} from the center of the cluster and centered on RA=08:40:36 and DE=-53:02:00 (Figure 1). The optical observations were carried out in four runs with the Wide Field Image (WFI) on the 2.2m telescope at La Silla in: 1999 January 24-February 9, 2000 January 20-24, 2007 March 10-23, and 2007 May 15-18. The deep fields in our survey were observed in four medium bands filters, namely, 770/19, 815/20, 856/14, and 914/27 (where the filter name notation is central wavelength on the full width at half-maximum, FWHM, in nm) and one broadband filter, Rc. We also observed all radial fields, including the outward fields, in the J band using the CPAPIR on the 1.5m telescope at Cerro Tololo, Chile (runs on 2007 February 28-March 3 and 2007 March 10). The J filter of CPAPIR is centered at 1250nm with a FWHM of 160nm. The spectroscopic observations were carried out with HYDRA, a multi-object, fiber-fed spectrograph on the 4m telescope at Cerro Tololo on the nights of 2007 January 6 and 7. Only two fields could be observed: the deep fields 15 and 20 with a coverage of 6429-8760{AA} centered at 7593{AA} and a spectral resolution of 4.0{AA}. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 91 3111 All photometric candidates of our survey table3.dat 96 10 Photometric candidates already detected by previous studies (table corrected by the author) table4.dat 77 17 Stellar parameters from the objects observed in our spectroscopic follow-up table6.dat 55 17 Spectroscopic data, photometric and spectroscopic membership status -------------------------------------------------------------------------------- See also: J/A+A/501/553 : Equivalent widths of IC 2602 + IC 2391 stars (D'Orazi+, 2009) J/A+A/461/509 : Membership and spectroscopy of IC 2391 (Platais+, 2007) J/A+A/468/151 : Nearby open clusters radii and masses (Piskunov+, 2007) J/A+A/430/287 : XMM observations of IC 2391 stars (Marino+, 2005) J/MNRAS/355/959 : Proper motions of IC 2391 possible members (Dodd+, 2004) J/A+A/372/862 : Lithium abundances in IC 2602 and IC 2391 (Randich+, 2001) J/ApJS/134/103 : Low-mass members of IC 2391 (Barrado y Navascues+, 2001) J/A+A/345/471 : Memberships of open clusters (Robichon+, 1999) J/A+AS/126/357 : Members of IC 2391 (Rolleston+ 1997) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- Field Field number 4- 6 I3 --- ID Running identification number 8 I1 h RAh Hour of Right Ascension (J2000) 10- 11 I2 min RAm Minute of Right Ascension (J2000) 13- 18 F6.3 s RAs Second of Right Ascension (J2000) 20 A1 --- DE- Sign of the Declination (J2000) 21- 22 I2 deg DEd Degree of Declination (J2000) 24- 25 I2 arcmin DEm Arcminute of Declination (J2000) 27- 31 F5.2 arcsec DEs Arcsecond of Declination (J2000) 33- 38 F6.3 mag Rmag ? Observed WFI R_c_ band magnitude 40- 45 F6.3 mag O770/19 ? Observed 770/19 medium band magnitude (G1) 47- 52 F6.3 mag O815/20 Observed 815/20 medium band magnitude (G1) 54- 59 F6.3 mag O856/14 ? Observed 856/14 medium band magnitude (G1) 61- 66 F6.3 mag O914/27 Observed 914/27 medium band magnitude (G1) 68- 73 F6.3 mag Jmag ? Observed CPARIR Johnson J-band magnitude 75- 79 F5.3 Msun Mass Mass (1) 81- 84 I4 K Teff Effective temperature (1) 86- 91 F6.3 mag P815/20 Predicted 815/20 medium band magnitude (2) -------------------------------------------------------------------------------- Note (1): The error on the determination of masses and effective temperature are: * {Delta}T_eff_=140K and {Delta}M=0.1M_{sun}_ for stars (M>0.2 M_{sun}_), * {Delta}T_eff_=230K and {Delta}M=0.05M_{sun}_ for very low mass star (VLMS) (0.072 in Simbad), CTIO objects are from Barrado y Navascues et al. (2004ApJ...614..386B; in Simbad), object 155 is from Dodd (2004, Cat. J/MNRAS/355/959; in Simbad) while the 2XMM objects are from XMM-Newton. The values of Ic, (R-I)c, and T_eff_ given in the last three columns are taken from each of the previous studies. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- Field [15/20] Field number 4- 6 I3 --- ID Running identification number 8 I1 h RAh Hour of right ascension (J2000) 10- 11 I2 min RAm Minute of right ascension (J2000) 13- 18 F6.3 s RAs Second of right ascension (J2000) 20 A1 --- DE- Sign of declination (J2000) 21- 22 I2 deg DEd Degree of declination (J2000) 24- 25 I2 arcmin DEm Arcminute of declination (J2000) 27- 31 F5.2 arcsec DEs Arcsecond of declination (J2000) 33- 36 F4.1 --- S/N Signal to noise ratio 38- 41 A4 --- SpT MK spectral type 43- 46 I4 K Teff Effective temperature (1) 48- 52 F5.3 Msun Mass Mass (1) 54- 59 F6.3 mag O815/20 Observed 815/20 medium band magnitude (G1) 61- 64 I4 K Tph Photometric effective temperature 66- 70 F5.3 Msun Mph Photometric mass 72- 77 F6.3 mag P815/20 Predicted 815/20 medium band magnitude -------------------------------------------------------------------------------- Note (1): The errors on the determination of masses and effective temperature based on spectroscopy are: * {Delta}T_eff_=190K and {Delta}M=0.03M_{sun}_ for spectra with S/N>10 (for an error of 1 subclass) * {Delta}T_eff_=320K and {Delta}M=0.04M_{sun} for spectra with 5 in Simbad. History: Tables 2, 4 and 6: From electronic version of the journal Table 3: corrected version by Steve Boudreault. ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Dec-2011