Surface brightness fluctuation distances for nearby dwarf elliptical galaxies
Surface brightness fluctuation distances for nearby dwarf elliptical galaxies
复制标题
附近矮椭圆星系的表面亮度涨落距离
DOI：
10.1051/0004-6361:20011408
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发表时间：
2001
影响因子：
6.5
通讯作者：
M. Valtonen
中科院分区：
文献类型：
--
作者：
H. Jerjen;R. Rekola;L. Takalo;M. Coleman;M. Valtonen
我们在北欧光学望远镜上获得了矮椭圆 (dE) 星系 DDO 44、UGC 4998、KK98 77、DDO 71、DDO 113 和 UGC 7356 的深 B 和 R 波段 CCD 图像。利用傅里叶分析技术，我们测量了星系 29 个不同区域的恒星 R 波段表面亮度涨落 (SBF) 和星等。 DDO 44、KK98 77、DDO 71 的红巨星分支距离的独立尖端用于将其视在星等集转换为绝对 SBF 星等。结果与相应的局部 (B R) 颜色相结合，并与使用 Padova 等时线的 Worthey 星族合成模型预测的主要古老、贫金属恒星族群的 (B R) MR 关系进行比较。虽然理论关系的颜色依赖性得到了经验数据的证实，但我们发现观察结果和理论之间存在系统性的零点偏移，因为模型在 0:13 (0:02) mag 上太微弱了。基于这些发现，我们建立了新的 SBF 方法半经验校准作为 dE 星系的距离指示器，估计不确定度为 10%。首先利用改进的校准，我们确定了其他三个早期型矮星 UGC 4998、DDO 113 和 UGC 7356 的 SBF 距离。虽然在 M 81 群区域中发现，但之前的速度测量表明 UGC 4998 是一个背景星系。该图片由我们的 SBF 距离 10: 5( 0:9) Mpc 确认。我们可以进一步将 DDO 113 识别为位于 Canes Venatici I (CVn I) 云近侧、距离 3:1(0:3) Mpc 的微弱恒星系统。我们样本中的第二个 CVn I 成员 UGC 7356 位于 6:7(0:6) Mpc 处，在空间上接近 NGC 4258 (M 106)。我们推导出所有矮星的 BR 表面亮度曲线和颜色梯度，并确定光度和 S ersic 参数。最后，我们讨论 DDO 71 和 UGC 7356 中的两个可能类似于球状星团的非恒星天体。
We obtained deepB andR-band CCD images for the dwarf elliptical (dE) galaxies DDO 44, UGC 4998, KK98 77, DDO 71, DDO 113, and UGC 7356 at the Nordic Optical Telescope. Employing Fourier analysis technique we measure stellar R-band surface brightness fluctuations (SBFs) and magnitudes in 29 dierent elds of the galaxies. Independent tip of the red giant branch distances for DDO 44, KK98 77, DDO 71 are used to convert their set of apparent into absolute SBF magnitudes. The results are combined with the corresponding local (B R) colours and compared with the (B R) MR relation for mainly old, metal-poor stellar populations as predicted by Worthey's population synthesis models using Padova isochrones. While the colour dependency of the theoretical relation is conrmed by the empirical data, we nd a systematic zero point oset between observations and theory in the sense that models are too faint by 0:13 (0:02) mag. Based on these ndings we establish a new semiempirical calibration of the SBF method as distance indicator for dE galaxies with an estimated uncertainty of10%. Taking rst advantage of the improved calibration, we determine SBF distances for the other three early-type dwarfs UGC 4998, DDO 113, and UGC 7356. Although found in the M 81 group region, previous velocity measurements suggested UGC 4998 is a background galaxy. This picture is conrmed by our SBF distance of 10: 5( 0:9) Mpc. We can further identify DDO 113 as a faint stellar system at the near side of the Canes Venatici I (CVn I) cloud at a distance of 3: 1( 0:3) Mpc. The second CVn I member in our sample, UGC 7356, lies at 6: 7( 0:6) Mpc and spatially close to NGC 4258 (M 106). We derive BR surface brightness proles and colour gradients for all dwarfs and determine photometric and S ersic parameters. Finally, we discuss two non-stellar objects in DDO 71 and UGC 7356 which may resemble globular clusters.