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A modified method to calibrate photographic surface photometry of galaxies and nebulae
Abstract
A method for surface photometry of galaxies and nebulae on ordinary Sky
Atlas Schmidt plates or films is presented. Microphotometric
measurements of stellar images are used to calibrate the photographic
characteristic curves. The method is applied to the galaxy NGC 253 with
an accuracy better than + or -0.2 m. Isophotal contour maps and
luminosity profiles for the galaxy are shown.
... currently popular use of sensitometric spots has drawbacks too (e.g., Agnelli et al. 1979, Walterbos andKennicut 1987). The methods of Kormendy 1973, Agnelli et al. 1979, and Feitzinger et al. 1983 depend on the profiles of field stars. Simultaneous photoelectric photometry is often needed, and Feitzinger et al. 1983 show that morphology of type II detections is not easily achieved. ...
... The methods of Kormendy 1973, Agnelli et al. 1979, and Feitzinger et al. 1983 depend on the profiles of field stars. Simultaneous photoelectric photometry is often needed, and Feitzinger et al. 1983 show that morphology of type II detections is not easily achieved. The methods are limited by their assumptions and complexity, and exiguous in their solutions for sky brightness and extinction. ...
An examination is made of the problem posed by wide-angle photographic photometry, in order to extract a photometric-morphological history of Comet P/Halley. Photometric solutions are presently achieved over wide angles through a generalization of an assumption-free moment-sum method. Standard stars in the field allow a complete solution to be obtained for extinction, sky brightness, and the characteristic curve. After formulating Newton's method for the solution of the general nonlinear least-square problem, an implementation is undertaken for a canonical data set. Attention is given to the problem of random and systematic photometric errors.
Luminosity profiles derived from photographic surface photometry
measurements for 26 spiral galaxies are presented and analyzed with
regard to galactic structural parameters. The luminosity profiles, which
were obtained for 2592 photometric measurements for each of the
galaxies, are represented as elliptically averaged profiles. A
decomposition procedure based on a de Vaucouleurs law for the bulge and
a radial exponential law for the bulge is applied to obtain photometric
parameters for the disk and bulge separately, as well as accurate
inclinations and true bulge flattenings for some of the objects.
Comparison of the actual profiles with the decomposition models reveals
that departures from exponential disks generally occur when recent star
formation is limited to certain disk regions, or when some perturbing
feature such as a bar, companion or oval distortion is present. The
distributions of disk central surface brightness, disk scale length, and
true bulge flattening are compared with previous investigations, and it
is found that the bulge-to-disk ratio is related to Hubble type,
although with a scatter larger than observational uncertainties.
Finally, a comparison of the bulge-to-disk mass ratios for the present
spirals with those measured for S0s suggests the presence of intrinsic
differences between the disks of the two types.
New photoelectric UBV data are presented for about 60 stars down to V = 16 in 47 Tuc, 80 stars to V = 16.5 in NGC 6397 and 50 stars to V = 17.5 in NGC 288.
The 47 Tuc data agree well with recent work by Menzies, and indicate systematic errors in earlier photographic photometry;
the majority of the 47 Tuc horizontal branch stars occupy a very small clearly defined region of the C–M diagram. NGC 6397
has a narrow well-defined giant branch, with only a few possible asymptotic branch stars or red horizontal branch stars; there
are considerable systematic errors in the earlier RGO photographic photometry. NGC 288 is unusual in having a predominantly
blue horizontal branch but apparently high metallicity according to several criteria; its reddening is E(B−V) = 0.04 mag and its apparent distance modulus is (m−M) ≈ 14.5.
A comparison is made between these three clusters and two studied previously, ω Cen and NGC 6752, and four northern clusters studied extensively by Sandage. The interstellar reddenings, distances, ultraviolet
excesses and other parameters are derived. Various metallicity parameters correlate well together, but several clusters violate
the general correlation between metallicity and horizontal branch type by having purely blue horizontal branches irrespective
of metallicity. NGC 288 is the most extreme example of this class, of which M13 is the prototype.
Detailed isophotometry of NGC 253 in the Sculptor Group in blue light
to a limiting surface brightness of 29 mag arcsec-2 has
been obtained from a combination of photographic and photoelectric
photometry. The standard photometric parameters have been derived; in
particular, the total magnitude is BT = 8.05, and the
maximum detected dimensions are 60' × 26', or 44 x 19 kpc at the
assumed distance of 2.5 Mpc. The absolute luminosity of NGC 253,
corrected for galactic and internal extinction is LT = 2.65
× 1010 Lsun. A three component luminosity
model of NGC 253 is derived consisting of a r1/4 spheroid,
an exponential disk, and the spiral arms, which contribute,
respectively, 15, 59, and 26% of the total B luminosity.
Detailed iosophotometry of NGC 253 in the Sculptor Group in blue light
to a limiting surface brightness of 29 magnitudes per square second was
obtained from a combination of photographic and photoelectric
photometry. The standard photometric parameters were derived. The
absolute luminosity of NGC 253, corrected for galactic and internal
extinction is LT = 2.65 x 10 to the 10th power L circle dot.
A three component luminosity model of NGC 253 is derived consisting of a
r to the 1/4th power spheroid, an exponential disk and a spiral arm
component which contribute, respectively, 15, 59, and 26 percent of the
total B luminosity. A detailed velocity map was derived from 9,842
individual radial velocity measurements on 25 H alpha interferograms
convering the entire bright disk. A total mass is estimated and
noncircular motions, in excess of 50 km/s, are observed in several
areas.