Intermediate-Band Surface Photometry of the Edge-on Galaxy NGC 4565

Abstract

We present a deep, 42.79 hr image of the nearby, edge-on galaxy NGC 4565 in the Beijing-Arizona-Taipei-Connecticut (BATC) 6660Å band using the large-format CCD system on the 0.6m Schmidt telescope at the Xinglong Station of the National Astronomical Observatories of China (NAOC). Following the procedures previously developed by our team for the analysis of deep images of galaxies (Zheng et al.), we obtain a final image that is calibrated to an accuracy of 0.02 mag in zero point, and for which we can measure galaxy surface brightness to an accuracy of 0.25 mag at a surface brightness at 27.5 mag arcsec −2 at 6660Å, corresponding to a distance of 22 kpc from the center of the disk. The integrated magnitude of NGC 4565 in our filter is m 6660 = 8.99 (= R magnitude of 9.1) to a surface brightness of 28 mag arcsec −2 . We analyze the faint outer parts of this galaxy using a two-dimensional model comprised of three components: an exponential thin disk, an exponential thick disk, and a power-law halo. Combined with a need to provide a cut-off radius for the disk, a total of 12 parameters are included in our model.We determine the best values of our model parameters via 10,000 random initial values, 3,700 of which converge to final values. We then plot the χ 2 for each converged fit versus parameter value for each of the 12 parameters. The thin disk and thick disk parameters we determine here are consistent with those of previous studies of this galaxy. However, our very deep image permits a better determination of the power law fit to the halo, constraining this power law to be between r −3.2 and r −4.0 , with a best fit value of r −3.88 . We find the axis ratio of the halo to be 0.44 and its core radius to be 14.4 kpc (for an adopted distance of 14.5 Mpc). We also agree with others that the bulge of NGC 4565 is fit well by an exponential luminosity distribution with scale height similar to that found for the thin disk.

Truncations of stellar disks and warps of HI-layers in edge-on spiral galaxies

“…The existence of the truncations -and the values for scale parameters (scalelength and scaleheight) of these stellar disks -and the associated truncation radii were confirmed to good or exellent precision using CCD photometry by Morrison et al (1994) for NGC 5907, by Fry et al (1999) for NGC 4244, by Morrison et al (1997) and Xilouris et al (1998) for NGC 891 and by Wu et al (2002) for NGC 4565.…”

“…7 in García-Ruiz et al 2002) in of the rotation curve at the positions of the onset of the warps for the galaxies in Table 4. Wu et al 2002) in the same direction as in the HI. NGC 5023 is a dwarf galaxy with the weakest evidence for a truncation in the stellar disk among these galaxies.…”

Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths

“…2 for the notations). Observations are shown for samples of late-type spirals (Yoachim & Dalcanton 2006, solid black and open circles), (Wu et al 2002;Abe et al 1999;Neeser et al 2002, diamond and triangles), a sample of early type galaxies (Pohlen et al 2004, diamond with a cross) and the Milky Way (Larsen & Humphreys 2003, square). In addition, a cosmological simulation is shown (from Brook et al 2004, asterisk). gradients (e.g., Shields 1990), they do not constitute a stringent test of the merger hypothesis, given the dependence on the preexisting disk and the strong mixing expected.…”

The influence of diffuse scattered light

“…Except PSF S09 and PSF A14 , the outer PSF (where r > ∼ 500 ) was measured once in the early eighties (PSF CV ), and only thrice before that (PSF K71 , PSF K73 , and PSF P73 ). Additionally, Wu et al (2002) claim that they measured a PSF that extends to r = 1700 , but they do not present it (and the data are lost, H. Wu, priv. comm.).…”