Surface Photometry of NGC 3 Lenticular Galaxy

Lenticular galaxy NGC3 has been chosen to study the surface photometry using griz filter. The data where obtained from the seventh Sloan Digital Sky Survey (SDSS) Data Release seven (DR7), and main the image reduction was done by the pipeline of SDSS. The work was achieved by the ELLIPS task from the STSDAS ISOPHOTE package in the Image Reduction and Analysis Facility (IRAF).The overall structure of the galaxy (a bulge, a bar, isophotal contour maps, together with a bulge to disk decomposition of the galaxy images where achieved, Also, the photometric properties (the disk position angle, ellipticity, B4 and inclination of the galaxy) where estimated.


Introduction
Surface photometry is one of the oldest techniques in the modern astronomy used to determine the surface brightness of extended objects such as galaxies and ionized hydrogen regions. The data from surface photometry are usually combined with those from kinematical observations to yield useful results and information about the structure, formation, and evolution of galaxies [1].
From surface photometry in several pass bands we can derive the colors of galaxies which provide information about the ages and the metal content of the stellar populations in the galaxies by using stellar population models [2].
SDSS Data Release seven (DR7) is an spectroscopic and imaging scanning of the celestial sphere [3] utilizing a devoted wide-field 2.5m optical telescope, in New Mexico,Apache Point Observatory [4].
Iraqi Journal of Science, 2019, Vol.60, No.9, pp: 2080-2086 1802 NGC 3 galaxy was in Pisces constellation (The Fishes). NGC 3 also known as ARAK 1, CGCG 408-35, IRAS 00047+0801, MCG 1-1-37, PGC 565, UGC 58 according to HyperLEDA and NASA/ IPACK Extragalactic Database (NED). NGC3 was possibly a lenticular galaxy, High-surfacebrightness galaxy [5], with a classification of S0 [6]. In this paper, The sections have been arranged as follows, at begging data reduction and method will explain, also, morphologies behavior and contour map of NGC 3 … will present, and then, the results and discussion will be presented and finally, the conclusions of this work will be summarized.

Data Reduction and Methods
In this technique, the fitting of the lenticular galaxy's isophotes to ellipses was achieved by using the ELLIPS task in the (STSDAS Library) in the Image Reduction and Analysis Facility (IRAF) [7]. The radial profiles of galaxy's surface brightness, ellipticity of the galaxy, position angle of the majoraxis and the parameter for isophotal shape (B4) can be determined after fitted the isophotal shape of the lenticular galaxy's isophotes to ellipses. Surface photometric analysis was applied by fitting elliptical contours to each sky-subtracted galaxy image. Some steps were done before the fitting process [8]: 1. Each pixel convert to arcsec (where 1 pixel = 0.396" for the Apache Point Observatory). 2. Dividing by the exposure time value (the value is the same for all filters, it equals to 53.907456 sec. 3. The counts to standard SDSS photometric system were converting by using the zero points, airmass, and extinction coefficient terms.

Morphologies Behavior and Contour Maps of NGC 3
Figure-1 shows the griz images of the NGC 3 galaxy. The NGC 3 galaxy has a disky shape of diameter about 40". The bulge is surrounded by a circular faint disk. The griz isophotal contour maps of NGC 3 are shown in Figure-

Results and Discussion a-Structural Profiles of NGC 3
The photometric properties, the disk position angle (PA), ellipticity of galaxy (ε=1−b/a), and the shape parameter (B4) of galaxy are estimated as a function of the radial distance from the center of the galaxy (r), and shown in Figures(4.3a, 3b, and 3c). It shows a symmetrical behavior in the various bands.
The disk position angle (PA) increases gradually from 121° at r=4" up to roughly 125" inside the bulge of galaxy and outer the nucleus of galaxy, then it becomes more or less to 111° at 22"), then it increase to about 125° (Figure-3a, and Table-2).
At the inner 4" region the ellipticity profiles of galaxy ( see Figure-(3b)) of NGC 3 rise from 0.32 to 0.55 at 7", where, in the disk region (r > 17") the ellipticity of galaxy becomes 0.34 as a mean value. The inclination of the disk of NGC 3 determined by used this mean value, which is around (0.43±0.09), in Eq. (1), and the result of Eq. 1 [9] showed that the NGC 3 galaxy inclined about 60 degrees.

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The parameter for isophotal shape B4 (Fourth harmonic of the Fourier expansion) profile showed in Figure-3c, and listed in Table-2, indicate that the NGC 3 galaxy is disky.

b-Decomposition of NGC 3
The least square fitting technique was used to decompose the griz luminosity profiles into the bulge, by using equation and disk of galaxy by using equations (2) and (3). [10] [ The outputs of the decomposition are listed in Table-3, and also illustrated in Figure-4 of griz bands. Freeman (1970) distinguished two types profile for the exponential disks [11], and from the results; the luminosity of griz filters explained that the disk of NGC 3 is of type II Freeman. Where LB T : band total brightness , re: Effective radius, : Effective surface brightness , B/D: bulge to disk ratio

Conclusions
We can conclude from the results, NGC 3 galaxy has a disky shape, with a bulge surrounded by a circular faint disk; it shows a symmetrical behavior with the various bands. From the photometric parameters, the inclination of the galaxy is about 60 degree, and from the shape parameter (B4), the disky system was confirmed. After the decomposition to a disk and bulge the luminosity of griz filters explained that the disk of NGC 3 is of type II Freeman.