CDROM/AJ/V113/P1011
UV Observations of the SMC (Cornett+ 1997)
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UIT: Ultraviolet Observations of the Small Magellanic Cloud
Robert H. Cornett, Michael R. Greason, Jesse K. Hill, Joel Wm.
Parker,
William H. Waller, Ralph C. Bohlin, Kwang-Peng Cheng, Susan G.
Neff,
Robert W. O'Connell, Morton S. Roberts, Andrew M. Smith
and Theodore P. Stecher
<1997, AJ, 113, 1011>
=1997AJ....113.1011C
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Abstract:
A mosaic of four UIT far-UV (FUV) (lambda_(eff)=1620 A) images, with
derived stellar and H II region photometry, is presented for most of
the Bar of the SMC. The UV morphology of the SMC's Bar shows that
recent star formation there has left striking features including: (a)
four concentrations of UV-bright stars spread from northeast to
southwest at nearly equal (~30 arcmin=0.5 kpc) spacings; (b) one of the
concentrations, near DEM 55, comprises a well-defined 8-arcmin diameter
ring surrounded by a larger H alpha ring, suggestive of sequential star
formation. FUV PSF photometry is obtained for 11,306 stars in the FUV
images, resulting in magnitudes m(162). We present a FUV luminosity
function for the SMC Bar, complete to m(162)~14.5. Detected objects are
well correlated with other SMC Population I material; of 711 H alpha
emission-line stars and small nebulae within the UIT fields of view,
520 are identified with FUV sources. The FUV photometry is compared
with available ground-based catalogs of supergiants, yielding 191
detections of 195 supergiants with spectral type earlier than F0 in the
UIT fields. The (m(162)-V) color for supergiants is a sensitive measure
of spectral type. The bluest observed colors for each type agree well
with colors computed from unreddened Galactic spectral atlas stars for
types earlier than about A0; for later spectral types the observed SMC
stars range significantly bluer, as predicted by comparison of
low-metallicity and Galactic-composition models. Redder colors for some
stars of all spectral types are attributed to the strong FUV extinction
arising from even small amounts of SMC dust. Internal SMC reddenings
are determined for all catalog stars. All stars with E(B-V)>0.15 are
within regions of visible H alpha emission. FUV photometry for 42 H
alpha -selected H II regions in the SMC Bar is obtained for stars and
for total emission (as measured in H II-region-sized apertures). The
flux-weighted average ratio of total to stellar FUV flux is 2.15;
consideration of the stellar FUV luminosity function indicates that
most of the excess total flux is due to scattered FUV radiation, rather
than stars fainter than m(162)=14.5. Both stellar and total emission
are well correlated with H alpha fluxes measured by Kennicutt and Hodge
[ApJ., 306, 130 (1986)], yielding FUV/H alpha flux ratios that are
consistent with models of SMC metallicity, ages from 1-5 Myr, and
moderate (E(B-V)=0.0-0.1 mag) internal SMC extinction. (Copyright) 1997
American Astronomical Society.
Description:
The table data were referred to, but did not appear in, the printed
paper.
File Summary:
------------------------------------------------------------------------------File Name
Lrecl
Records
Explanations
------------------------------------------------------------------------------table.dat
58
11306
NGC 147 - inner field photometry
------------------------------------------------------------------------------Byte-by-byte Description of file: table.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1- 5
I5
--Star
UIT star number
6- 7
I2
--Field
*UIT field number
8-14
F7.1
pix
X
X pixel coordinate (1 pix = 1.12
arcsec)
15-21
F7.1
pix
Y
Y pixel coordinate (1 pix = 1.12
arcsec)
22-25
I4
h
RAh
*Right ascension (2000)
26-28
I3
min
RAm
R.A.
29-33
F5.1
s
RAs
R.A.
34-35
2X
----Blank
36
A1
--DESign declination
37-38
I2
deg
DEd
Declination (2000)
39-41
I3
arcmin DEm
Dec.
42-44
I3
arcsec DEs
Dec.
45-51
F7.2
mag
m162
*m(162) derived from PSF photometry
52-58
F7.2
mag
e_m162
*Estimated error in m162
------------------------------------------------------------------------------Notes for file: table.dat
------------------------------------------------------------------------------Field:
Fields are 40 arcmin in diameter; locations of Fields 1, 2, 3,
and 4 are shown in the printed paper.
RAh:
Mean uncertainty in UIT positions is approximately 5 arcsec,
with smaller values near field centers (X=1023.5, Y=1023.5) and
larger values near the edges.
m162:
UIT magnitudes are defined by
m(lamda)=-2.5 log (F(lambda)) - 21.1
where F(lambda) is in units of ergs/(cm^2 Angstrom sec) and is
the mean flux per Angstrom over the UIT bandpass.
The magnitudes in this table are made with UIT's 'B5' bandpass,
which has an effective wavelength (for a flat input spectrum)
of 1620 Angstroms, and an effective width of 225 Angstroms.
These magnitudes are termed 'm(162)' (and occasionally 'm(B5)')
in the literature. More details on UIT hardware, observations,
and data reduction are in Stecher et al, ApJ 395, L1 (1992),
and in Stecher et al PASP 1997 (submitted October 1996).
e_m162:
This is the uncertainty returned by UITPHOT, an IDL/UIT
implementation of DAOPHOT which incorporates the noise
characteristics of UIT. It includes sky and other photometric
uncertainties, but no absolute calibration uncertainty. From
comparison with IUE spectra, the uncertainty in the absolute
calibration is about 0.15 for typical stars in this table.
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(End)
Lee Brotzman [ADS] 09Apr-1997