CDROM/APJ/V446/P622 UIT and Optical Imagery of LH 52 and LH 53 (Hill+ 1995) ================================================================================ UIT and Optical Imagery of Large Magellanic Cloud Associations LH 52 and LH 53: Ages and Initial Mass Function Slopes Robert S. Hill, K.-P. Cheng, Ralph C. Bohlin, Robert W. O'Connell, Morton S. Roberts, Andrew M. Smith, & Theodore P. Stecher <1995, ApJ, 446, 622> =1995ApJ...446..622H ================================================================================ Abstract: A 40' field including the stellar associations LH 52 and LH 53 and the supernova remnant N49 in the Large Magellanic Cloud was observed by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Space Shuttle mission in 1990 December. The image in the 162 nm bandpass is discussed together with ground-based BV data on subfields containing LH 52 and LH 53. Point-spread function photometry in the 162 nm, B, and V bands is presented in the form of color-magnitude diagrams and two-color diagrams, which are compared with stellar models. The far-ultraviolet extinction curve of the dust in LH 52 is unusually steep for the LMC. The most probable age of both associations is ~10 Myr, which constrains the scenario for the evolution of the supergiant Halpha shell LMC 4 by stochastic self-propagated star formation. The initial mass function (IMF) slope for LH 52 is Gamma ~ -1, in agreement with previous work, and the slope for LH 53, which is less densely populated, is Gamma ~ -2. A similar relationship between surface density of stars and IMF slope is reported for a UIT field near 30 Dor. The ultraviolet morphology of N49, which is contained in LH 53, is dominated by two bright features that straddle an X-ray bright spot, consistent with an encounter between the blast wave and a cloud. The estimated age of ~10 Myr for LH 53 implies an initial mass of ~20 Msun for the N49 progenitor star. Keywords: dust, extinction -- Magellanic Clouds -- open clusters and associations: individual (LH 52, LH 53) -- stars: luminosity function, mass function -- ultraviolet: stars File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 98 122 Ultraviolet sources in LH 52 table2.fit 2880 10 Author-supplied FITS version of table2.dat table3.dat 118 201 Ultraviolet sources in LH 53 table3.fit 2880 14 Author-supplied FITS version of table3.dat lh52_bv.dat 60 1048 BV photometry of LH 52 lh52_bv.fit 2880 26 Author-supplied FITS version of lh52_bv.dat lh53_bv.dat 60 2227 BV photometry of LH 53 lh53_bv.fit 2880 51 Author-supplied FITS version of lh53_bv.dat -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- ID *Identification 5- 7 I3 h RAh Right ascension, equinox J2000 8-10 I3 min RAm R.A. 11-16 F6.2 s RAs R.A. 17 1X --- --- Blank 18 A1 --- DE- Dec. Sign 19-20 I2 deg DEd Declination, equinox J2000 21-23 I3 arcmin DEm Dec. 24-28 F5.1 arcsec DEs Dec. 29-36 F8.2 mag m162 *Magnitude at 162 nm 37-44 F8.3 mag e_m162 DAOPHOT-type internal error in m162 45-52 F8.2 mag B Calibrated B magnitude 53-60 F8.3 mag e_B DAOPHOT-type internal error in B 61-68 F8.2 mag V Calibrated V magnitude 69-76 F8.3 mag e_V DAOPHOT-type internal error in V 77-98 A22 --- Remark Remark on dup. matches or UIT image quality -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- ID: IDs are derived from UIT photometry. Duplicates mean the same ultraviolet source had more than one candidate match on the B image, and the author could not decide between them. However, coordinates are based on the B sources and can thus differ between two appearances of the same ID. m162: m162 = -2.5*alog10(f_B5) - 21.1, where f_B5 is the mean flux in the UIT B5 bandpass in erg/cm2/s/A; the B5 centroid wavelength is approximately 162 nm. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- ID *Identification 5- 7 I3 h RAh Right ascension, equinox J2000 8-10 I3 min RAm R.A. 11-16 F6.2 s RAs R.A. 17 1X --- --- Blank 18 A1 --- DE- Dec. Sign 19-20 I2 deg DEd Declination, equinox J2000 21-23 I3 arcmin DEm Dec. 24-28 F5.1 arcsec DEs Dec. 29-36 F8.2 mag m162 *Magnitude at 162 nm 37-44 F8.3 mag e_m162 DAOPHOT-type internal error in m162 45-52 F8.2 mag B []?=99.99 Calibrated B magnitude 53-60 F8.3 mag e_B []?=99.999 DAOPHOT-type internal error in B 61-68 F8.2 mag V []?=99.99 Calibrated V magnitude 69-76 F8.3 mag e_V []?=99.999 DAOPHOT-type internal error in V 77-118 A42 --- Remark Remark on dup. matches or UIT image quality -------------------------------------------------------------------------------- Notes for file: table3.dat -------------------------------------------------------------------------------- ID: IDs are derived from UIT photometry. Duplicates mean the same ultraviolet source had more than one candidate match on the B image, and the author could not decide between them. However, coordinates are based on the B sources and can thus differ between two appearances of the same ID. m162: m162 = -2.5*alog10(f_B5) - 21.1, where f_B5 is the mean flux in the UIT B5 bandpass in erg/cm2/s/A; the B5 centroid wavelength is approximately 162 nm. -------------------------------------------------------------------------------- Byte-by-byte Description of file: lh52_bv.dat lh53_bv.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- ID Identification derived from V photometry 5- 7 I3 h RAh Right ascension, equinox J2000 8-10 I3 min RAm R.A. 11-16 F6.2 s RAs R.A. 17 1X --- --- Blank 18 A1 --- DE- Declination sign 19-20 I2 deg DEd Declination, equinox J2000 21-23 I3 arcmin DEm Dec. 24-28 F5.1 arcsec DEs Dec. 29-36 F8.2 mag B B magnitude 37-44 F8.3 mag e_B DAOPHOT-like internal error 45-52 F8.2 mag V V magnitude 53-60 F8.3 mag e_B DAOPHOT-like internal error -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 10-Oct-95