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J/ApJ/667/L145        HST Photometry of M82 region B      (Smith+, 2007)

The young cluster population of M82 region B. Smith L.J., Bastian N., Konstantopoulos I.S., Gallagher III J.S., Gieles M., De Grijs R., Larsen S.S., O'Connell R.W., Westmoquette M.S. <Astrophys. J., 667, L145-L149 (2007)> =2007ApJ...667L.145S
ADC_Keywords: Galaxies, nearby ; Associations, stellar ; Photometry, HST Keywords: galaxies: evolution - galaxies: individual (M82) - galaxies: photometry - galaxies: star clusters - galaxies: starburst Abstract: We present observations obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope of the "fossil" starburst region B in the nearby starburst galaxy M82. By comparing UBVI photometry with models, we derive ages and extinctions for 35 U-band-selected star clusters. We find that the peak epoch of cluster formation occurred ∼150Myr ago, in contrast to earlier work that found a peak formation age of 1.1Gyr. The difference is most likely due to our inclusion of U-band data, which are essential for accurate age determinations of young cluster populations. We further show that the previously reported turnover in the cluster luminosity function is probably due to the neglect of the effect of extended sources on the detection limit. The much younger cluster ages we derive clarifies the evolution of the M82 starburst. The M82-B age distribution now overlaps with the ages of the nuclear starburst, the clusters formed on the opposite side of the disk, and the last encounter with M81, some 220Myr ago. Description: Observations with the High Resolution Channel (HRC) of the ACS on board HST were made of region B on UT 2006 November 4 and 5 using the F330W (U) filter (proposal ID: 10853, PI: L. J. Smith). These observations were designed to be supplementary to the M82 mosaic obtained by the Hubble Heritage Team using the Wide Field Channel (WFC) of the ACS and the F435W (B), F555W (V), and F814W (I) filters. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 09 59.1 +69 27 M82 region B = [OM78] B 09 56 02.7 +69 41 10 M82 region B1 = [OM78] B1 09 55 57.2 +69 41 06 M82 region B2 = [OM78] B2 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 80 35 Photometry and derived parameters of the cluster sample in region B
See also: J/A+A/293/703 : Outflow in M82 halo (McKeith+, 1995) J/AJ/121/768 : BVIJH photometry of M82 (de Grijs+, 2001) J/ApJ/619/270 : Young super star clusters in M82 starburst (Melo+, 2005) J/MNRAS/391/1384 : Deep MERLIN 5GHz radio sources in M82 (Fenech+, 2008) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 --- [SBK2007] Running identification number 4- 8 F5.2 mag F330W HST/ACS F330W filter magnitude 10- 13 F4.2 mag e_F330W Uncertainty in F330W 15- 19 F5.2 mag F435W HST/ACS F435W filter magnitude 21- 24 F4.2 mag e_F435W Uncertainty in F435W 26- 30 F5.2 mag F555W HST/ACS F555W filter magnitude 32- 35 F4.2 mag e_F555W Uncertainty in F555W 37- 41 F5.2 mag F814W HST/ACS F814W filter magnitude 43- 46 F4.2 mag e_F814W Uncertainty in F814W 48- 50 F3.1 --- Chi ? Model χ2ν value 52- 55 F4.2 mag Emin ? Model minimum E(F435W-F555W) color index 57- 60 F4.2 mag Ebest ? Model best E(F435W-F555W) color index 62- 65 F4.2 mag Emax ? Model maximum E(F435W-F555W) color index 67- 70 F4.2 [yr] logAmin ? Model minimum log of the age 72- 75 F4.2 [yr] logA ? Model best log of the age 77- 80 F4.2 [yr] logAmax ? Model maximum log of the age
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 28-Nov-2009
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