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J/A+A/443/41    NGC 4038/4039 broad and /narrow band photometry  (Mengel+, 2005)

Star-formation in NGC 4038/4039 from broad- and narrow band photometry: Cluster Destruction? Mengel S., Lehnert M.D., Thatte N., Genzel R. <Astron. Astrophys. 443, 41 (2005)> =2005A&A...443...41M
ADC_Keywords: Associations, stellar ; Photometry Keywords: galaxies: star clusters - galaxies: individual: NGC 4038/4039 - galaxies: interaction Description: The Ks-band image which was used for the 3σ-detection was obtained with ISAAC on VLT-ANTU as part of programme 65.N-0577, and has a FWHM of ∼0.38". 1072 point-like objects were detected. For the multi-band photometry, we also used the HST archival images obtained by Whitmore et al. (see Whitmore et al., 1999AJ....118.1551W), which we rebinned to the same pixel size as the ISAAC image (0.1484"/pix). The CO narrow band image was also obtained with ISAAC, while the Brγ image was obtained with SOFI at the NTT (programme number 63.N-0528). The Brγ image had a lower image quality than the other two images (FWHM=0.7"). The photometry data were used to simultaneously fit age and extinction for each individual cluster in comparison to an evolutionary synthesis model. Where possible, the visual extinction was determined from an average of the extinction from the broadband fit and from the Hydrogen recombination line ratios (in comparison to the expected Case B line ratio). The age estimate from the fit was, where possible, averaged with the aged determined from equivalent widths and CO index. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table.dat 105 1072 Broad- and narrow-band photometry
See also: J/AJ/109/960 : Young star clusters in The Antennae (Whitmore+ 1995) J/AJ/124/1418 : Radio-optical identification of star clusters (Whitmore+ 2002) J/AJ/127/660 : Photometry in southern tail of the Antennae (Saviane+, 2004) J/ApJ/561/727 : BVI photometry in the Antennae galaxies (Zhang+, 2001) J/ApJ/599/1049 : Supergiant molecular complexes in the Antennae (Wilson+, 2003) Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 6 F6.2 arcsec dRA Distance in RA to RA = 12 01 52.97 (1) 8- 13 F6.2 arcsec dDE Distance in DE to DE = -18 52 08.29 (1) 15- 19 F5.2 mag Umag ? Apparent Johnson U magnitude (2) 21- 25 F5.2 mag Bmag ? Apparent Johnson B magnitude (2) 27- 31 F5.2 mag Vmag ? Apparent Johnson V magnitude (2) 33- 37 F5.2 mag Imag ? Apparent Cousins I magnitude (2) 39- 43 F5.2 mag Ksmag Apparent Ks magnitude (2) 45- 51 F7.2 0.1nm EWHa ? Equivalent width of Halpha (3) 53- 58 F6.2 0.1nm EWBrg ? Equivalent width of Brgamma (4) 60- 64 F5.2 mag COindex ? CO index (5) 66- 70 F5.2 mag AV ? Visual extinction (6) 72- 77 F6.2 Myr Age Age (7) 79- 81 F3.1 --- q_Age Quality of the age estimate (8) 83- 88 F6.2 10+5solMass Massph Photometric mass (9) 90- 94 F5.1 pix Dist Distance to nearest cluster (10) 96-105 A10 --- Cross-ID Cross-Identification (11)
Note (1): The reference position (deltaRA, deltaDec = 0,0) we are using is the same as that used in Whitmore et al., 1999AJ....118.1551W, namely: RA = 12 01 52.97, DE = -18 52 08.29 (J2000) Note (2): Magnitudes are not extinction corrected. Aperture correction using a fixed value (0.7(0.5)mag for V(Ks)) from a fixed aperture (5(3)pix for V(Ks)) was applied if the closest neighbour was closer than 10(12) pixels (for V(Ks) band) (see column 15). For isolated clusters, the total apparent cluster magnitude was determined by a curve-of-growth technique. Only the magnitudes for V and Ks-band were determined directly. U, B, and I magnitudes were determined from the difference to the V band in an aperture of r=3pix. Note (3): The continuum flux was determined from an interpolation of the V and the I band for the wavelength of Halpha in NGC 4038/4039. The equivalent width was determined from a small aperture (r=3pix) which, for clusters with extended shells, underestimates the total Hα flux. Note (4): The Brγ SOFI image had a lower image quality than the Ks-band ISAAC image. In order to determine the continuum flux for a given cluster, the Ks-image was degraded to a comparable FWHM (0.7" for the SOFI image, as opposed to 0.38" for the ISAAC image). Note (5): We constructed our CO index from the difference in magnitudes (for an aperture with r=5pix) between the ESO CO2.34 narrow band filter and the Ks filter. This value is not extinction corrected. Note (6): Visual foreground screen extinction. Determined, where applicable, from an average of the extinction determined from the broadband fit and the extinction from the line ratios. Note (7): Age determined in comparison to the Starburst99 evolutionary synthesis model (Leitherer et al., 1999ApJS..123....3L), for an instantaneous burst, solar metallicity, Salpeter IMF between 1 and 100M. The value reported in this column is, where possible, an average of the four age indicators that may be present: Fit to the broadband colours, WHa, WBrg and COindex. See also the column q_Age for the reliability of the age estimate. Note (8): This (arbitrary value) parameter indicates the quality of the age determination. The higher the number (4.0 being highest), the more reliable the assigned cluster age. 3.0 and higher show reasonable to good agreement, 1.5 and lower show severe disagreement in at least one age indicator and should be treated with caution (they were excluded from the analysis in the paper). Note (9): Photometric mass of the cluster, determined from the extinction corrected K-band magnitude, in combination with the age. Note the model assumptions which influence this value quoted in Note (7), particularly IMF slope and mass cutoffs. Note (10): Distance in pixels to the nearest cluster which was also detected in Ks-band. This parameter is used for the decision which method to use to determine the total magnitude of the cluster (see Note (2)). Note (11): Cross-identification of a few clusters and stars with objects listed in Whitmore et al., 1999AJ....118.1551W (W99, W99-N = [WZL99] 1- N, W99-StarN = [WZL99] 4- N in Simbad) and in Whitmore & Schweizer, 1995, Cat. J/AJ/109/960 (WS95, [WS95] NNN in Simbad). Magnitudes differ for some objects, most likely due to different aperture corrections (see also detailed analysis of surface brightness profiles for three clusters in W99, Sec. 4.4.2).
Acknowledgements: Sabine Mengel, smengel(at)
(End) Patricia Vannier [CDS] 02-Jun-2005
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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