J/AJ/125/1696 Star-forming knots in NGC 3395/3396 (Hancock+, 2003)
Star-forming knots in the UV-bright interacting galaxies NGC 3395 and NGC 3396.
Hancock M., Weistrop D., Eggers D., Nelson C.H.
<Astron. J. 125, 1696 (2003)>
=2003AJ....125.1696H 2003AJ....125.1696H
ADC_Keywords: Galaxies, photometry ; Photometry, ultraviolet
Keywords: galaxies: individual (NGC 3395, NGC 3396) - galaxies: interactions -
galaxies: starburst - galaxies: star clusters
Abstract:
We have obtained ultraviolet and visible wavelength images for the
central regions of the interacting galaxies NGC 3395 and NGC 3396,
using the Space Telescope Imaging Spectrograph on the Hubble Space
Telescope. The images show many isolated sources of ultraviolet
emission produced by young star-forming regions (knots). The FWHM of
most of the knots in both galaxies is ≤20pc. Far-UV flux
distributions for the complete sample of knots can be fitted with a
power law with exponent α=-1.20±0.35 for NGC 3395 and a power
law with exponent α=-0.69±0.21 for NGC 3396. Comparison with
models from Leitherer et al. indicates that the ages of most of the
knots are ≤80Myr. Reddening of the knots ranges from E(B-V)=0.0 to
E(B-V)=0.3mag, indicating variable amounts of dust in these regions.
Almost all the knots have masses less than 106M☉. Many of the
knots are probably bound and at least six knots are good
proto-globular cluster candidates. There are no significant
differences in the fluxes, sizes, and ages of the knots in the two
galaxies. The average mass of the knots in NGC 3395 is an order of
magnitude less than the average mass of the knots in NGC 3396. There
is no obvious correlation between the age of a knot and its position
the galaxy.
Description:
Ultraviolet and visible wavelength images for the interacting galaxies
NGC 3395 and NGC 3396 were obtained using the Space Telescope Imaging
Spectrograph (STIS) on HST. Table 1 contains a description of the
observations, including the detector and filter wavelength
characteristics.
Objects:
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RA (2000) DE Designation(s)
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10 49 50.1 +32 59 57 NGC 3395
10 49 55.3 +32 59 26 NGC 3396
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 86 66 NGC 3395 data
table3.dat 86 51 NGC 3396 data
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Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Num Knot number (1)
4 A1 --- f_Num [*] Indicates not in the complete sample
5- 9 F5.1 arcsec EOff East offset from the image center
11- 15 F5.1 arcsec NOff North offset from the image center
17- 24 E8.2 10mW/m2/nm MCCD Measured F28X50LP band aperture flux (2)
26- 33 E8.2 10mW/m2/nm CCCD Corrected F28X50LP band aperture flux (2)
35- 42 E8.2 10mW/m2/nm MFUV Measured F25QTZ band aperture flux (2)
44- 51 E8.2 10mW/m2/nm CFUV Corrected F25QTZ band aperture flux (2)
53- 60 E8.2 10mW/m2/nm MNUV Measured F25CN182 band aperture flux (2)
62- 69 E8.2 10mW/m2/nm CNUV Corrected F25CN182 band aperture flux (2)
71- 74 F4.2 [---] log(FUV/CCD) Log of the FUV to CCD fluxes
76- 80 F5.2 [---] log(FUV/NUV) Log of the FUV to NUV fluxes
82- 85 F4.1 pix FWHM Knot FUV full width at half-maximum
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Note (1): Table 2: [HWE2003] NGC 3395 NN
Table 3: [HWE2003] NGC 3396 NN
Note (2): in units of ergs/s/cm2/Angstroem.
Filter information from Table 1:
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Filter Detector lambda central FWHM Exp.Time UT Date of Observation
Å Å s NGC 3395 NGC 3396
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F25QTZ FUV MAMA 1595 206 1000 1998/05/07 1998/05/28
F25CN182 NUV MAMA 2010 681 814 1998/05/07 1998/05/28
F28X50LP CCD 7230 1998 300 1998/05/07 1998/05/28
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 22-May-2003