Volume 581, September 2015
|Number of page(s)||8|
|Published online||08 September 2015|
The data reduction and analysis were conducted using the MIDAS package. First, all images were cleaned of all foreground and background objects. Then we used the SURFPHOT program from the MIDAS package to perform all the steps of the photometric procedure: the sky background subtraction, the subsequent ellipse fitting and integration of the light in the obtained ellipses. The algorithm of this software is based on the formulas of Bender (1987) and Bender & Moellenhoff (1987). The FIT/FLAT_SKY task was used to approximate the sky background by a surface created with a two-dimensional
polynomial and the least-squares method. All pixels of the residual image with values that differed by more than two sigma from the mean value of the sky were not used in the calculation of the background level with the FIT/BACKGROUND program. The typical accuracy of the sky brightness estimation was better than 1%. This corresponds to the level SB ~ 27–28 mag arcsec-2 in the B band. The ellipse fitting was carried out using the sky-subtracted images and the task FIT/ELL3. The INTEGRATE/ELLIPSE program was used to integrate the light in the successive ellipses. To transform SDSS magnitudes into the Johnson-Cousins system, we used the empirical color transformations by Jordi et al. (2006).
SDSS images of the three dSphs KKH 65, KK 180, and KK 227 (from left to right).
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Surface photometry using SDSS images in the g, r, i bands and Sersic function fitting results for KKH 65, KK 180, and KK 227.
Sersic function fits to the equivalent profiles of KKH 65 in the B, V, R, I bands.
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The algorithm developed by MK11 identified eight members of the NGC 3414 group. Using the same group-finding algorithm and new observational data (radial velocities from SDSS DR9 and spectroscopic and photometric data for KKH 65), we found 19 galaxies with differences in radial velocities smaller than 600 km s-1 and within the projected radius from NGC 3414 kpc (Table B.1). Eleven of them are members of the group with ii< 1, and eight objects are candidate field galaxies with ii> 1. Some of log (ii) values are close to zero. This means that the actual group size may change if accurate redshift-independent distances will be available. After selecting the group members, we compared the properties of KKH 65 and the surrounding galaxies. There are three candidate early-type group member galaxies fainter than KKH 65, and six candidate field early-type objects comparable to KKH 65 (Table B.1). SDSS images and our photometric study indicate that KKH 65 is the most diffuse among all these objects.
Table B.1 lists the data for the projected neighbors of KKH 65 with the differences in radial velocities between NGC 3414 and each individual galaxy that are smaller than 600 kms-1: (1) galaxy name; (2) equatorial coordinates; (3) morphological type in numerical code according to the RC3 catalog (de Vaucouleurs et al. 1991); (4) integrated magnitude in the Ks band, corrected for Galactic extinction; (5) radial velocity with respect to the centroid of the LG; (6) projected separation in kpc from NGC 3414 assuming that the galaxies are located at their Hubble distances; (7) logarithmic isolation index calculated with respect to NGC 3414 calculated according to MK11.
Table B.2 lists galaxies located within the projected vicinity from KK 180. The results of the MK11 algorithm (Table B.2) favor an extremely weak gravitational influence between the UGC 8036 group members. At the same time, the gravitational attraction from the Virgo cluster is strong. (1) Galaxy name; (2) equatorial coordinates; (3) morphological type in numerical code according to de Vaucouleurs et al. (1991); (4) integrated magnitude in the Ks band; (5) radial velocity with respect to the centroid of the LG; (8) projected separation in kpc from UGC 8036; (9) isolation index with respect to UGC 8036; (10) projected separation in Mpc from M 87; (11) isolation index calculated with respect to the center of the Virgo cluster with the total mass of 8 × 1014M⊙ (Karachentsev et al. 2014). The projected separations are calculated assuming that the galaxies are at their Hubble distances.
S0 galaxy NGC 3414 and galaxies with differences in radial velocities smaller than 600 km s-1 and within the projected radius from NGC 3414 kpc.
Most massive galaxy in the Virgo cluster M 87 and six galaxies around KK 180 with a radial velocity difference smaller than km s-1 and within the projected radius from KK180 kpc.
The long-slit observations revealed a distant extended object seen through the stellar body of KK 227 with a QSO-like spectrum. It was detected in both slit positions. We estimated its redshift z = 0.535 using only one clearly seen line MgII 2798 Å. The orientation of the slit in the case of KK 227 and the location of the quasar are shown in Fig. C.1.
Left: settings of the slit on the preliminary short-exposure image of KK 227 in the B band. The approximate location of a quasar is circled. Right: one-dimensional total spectrum of the quasar after observations in the two positions of the slit.
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© ESO, 2015
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