Enhanced dust heating in the bulges of early-type spiral galaxies
C. W. Engelbracht, L. K. Hunt, R. A. Skibba, J. L. Hinz, D. Calzetti, K. D. Gordon, H. Roussel, A. F. Crocker, K. A. Misselt, A. D. Bolatto, R. C. Kennicutt, P.… 展开作者
C. W. Engelbracht, L. K. Hunt, R. A. Skibba, J. L. Hinz, D. Calzetti, K. D. Gordon, H. Roussel, A. F. Crocker, K. A. Misselt, A. D. Bolatto, R. C. Kennicutt, P. N. Appleton, L. Armus, P. Beirão, B. R. Brandl, K. V. Croxall, D. A. Dale, B. T. Draine, G. Dumas, A. Gil de Paz, B. Groves, C. -N. Hao, B. D. Johnson, J. Koda, O. Krause, A. K. Leroy, S. E. Meidt, E. J. Murphy, N. Rahman, H. -W. Rix, K. M. Sandstrom, M. Sauvage, E. Schinnerer, J. -D. T. Smith, S. Srinivasan, L. Vigroux, F. Walter, B. E. Warren, C. D. Wilson, M. G. Wolfire, S. Zibetti
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Accepted for publication on the A&A Herschel Special Issue
Stellar density and bar strength should affect the temperatures of the cool (T ~ 20-30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 microns. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of the Herschel observations for the KINGFISH (key insights in nearby galaxies: a far-infrared survey with Herschel) sample. We fit single-temperature modified blackbodies to far-infrared and submillimeter measurements of the central and disk regions of galaxies to determine the temperature of the component(s) emitting at those wavelengths. We present the ratio of central-region-to-disk-temperatures of the cool dust component of 13 nearby galaxies as a function of morphological type. We find a significant temperature gradient in the cool dust component in all galaxies, with a mean center-to-disk temperature ratio of 1.15 +/- 0.03. The cool dust temperatures in the central ~3 kpc of nearby galaxies are 23(+/-3)% hotter for morphological types earlier than Sc, and only 9(+/-3)% hotter for later types. The temperature ratio is also correlated with bar strength, with only strongly barred galaxies having a ratio over 1.2. The strong radiation field in the high stellar density of a galactic bulge tends to heat the cool dust component to higher temperatures, at least in early-type spirals with relatively large bulges, especially when paired with a strong bar.
The similar stellar populations of quiescent spiral and elliptical galaxies
我们比较了星系动物园和SDSS DR 7中视觉分类的非恒星形成螺旋星系和椭圆星系中心区域的恒星星族特性。这些星系位于红移范围$0.04<z<0.1$内，恒星质量大于$logM_*=10.4$。我们只选择正面的螺旋星系，以避免污染的光从光盘的SDSS光纤，使强大的视觉识别的螺旋结构。总的来说，我们发现，星系与较大的中央恒星速度色散，无论形态类型，有年龄较大，较高的金属丰度，和增加过剩的α-元素。年龄和α增强，在固定的速度分散，不依赖于形态类型。唯一的参数，在一个给定的速度色散，与形态类型相关的是金属丰度，在那里的螺旋星系的凸起的金属丰度是0.07德克斯高于椭圆星系。然而，对于具有给定总恒星质量的星系，这种对形态的依赖性消失了。假设，对于我们的样本，速度色散跟踪的质量单独的凸起，而不是总质量（凸起+磁盘）的星系，我们的研究结果意味着星系的形成时代和恒星形成期的持续时间与质量的凸起。金属保留在星系中的程度，而不是由于流出而被移除，由星系的总质量决定。
