The dust energy balance in the edge-on spiral galaxy NGC 4565
Ilse De Looze, Maarten Baes, George J. Bendo, Laure Ciesla, Luca Cortese, Gert De Geyter, Brent Groves, Médéric Boquien, Alessandro Boselli, Lena Brondeel, Asan… 展开作者
Ilse De Looze, Maarten Baes, George J. Bendo, Laure Ciesla, Luca Cortese, Gert De Geyter, Brent Groves, Médéric Boquien, Alessandro Boselli, Lena Brondeel, Asantha Cooray, Steve Eales, Jacopo Fritz, Frédéric Galliano, Gianfranco Gentile, Karl G. Gordon, Sacha Hony, Ka H. Law, Suzanne C. Madden, Marc Sauvage, Matthew W. L. Smith, Luigi Spinoglio, Joris Verstappen
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16 pages, 7 figures, accepted for publication in MNRAS
We combine new dust continuum observations of the edge-on spiral galaxy NGC 4565 in all Herschel/SPIRE (250, 350, 500 micron) wavebands, obtained as part of the Herschel Reference Survey, and a large set of ancillary data (Spitzer, SDSS, GALEX) to analyze its dust energy balance. We fit a radiative transfer model for the stars and dust to the optical maps with the fitting algorithm FitSKIRT. To account for the observed UV and mid-infrared emission, this initial model was supplemented with both obscured and unobscured star-forming regions. Even though these star-forming complexes provide an additional heating source for the dust, the far-infrared/submillimeter emission long wards of 100 micron is underestimated by a factor of 3-4. This inconsistency in the dust energy budget of NGC 4565 suggests that a sizable fraction (two-thirds) of the total dust reservoir (Mdust ~ 2.9e+8 Msun) consists of a clumpy distribution with no associated young stellar sources. The distribution of those dense dust clouds would be in such a way that they remain unresolved in current far-infrared/submillimeter observations and hardly comtribute to the attenuation at optical wavelengths. More than two-thirds of the dust heating in NGC 4565 is powered by the old stellar population, with localized embedded sources supplying the remaining dust heating in NGC 4565. The results from this detailed dust energy balance study in NGC 4565 is consistent with that of similar analyses of other edge-on spirals.
Molecular Gas of the Most Massive Spiral Galaxies I: a Case Study of NGC 5908
本文介绍了从CGM-MASS样品中选取的大质量旋涡星系NGC 5908的CO及其同位素的IRAM 30 m分子谱线观测结果。$^{12}$ CO $J=1-0$、$^{12}$ CO $J=2-1$和$^{13}$ CO $J=1-0$谱线在银河系盘的大多数位置都被探测到。NGC 5908的总分子气体质量是$\sim7\times10^9\rm~M_\odot$，加上原子氢的总冷气质量是$\sim1.3\times10^{10}\rm~M_\odot$，相当于晕中X射线发射热气的质量上限。用所有三条CO线构建的旋转曲线模型表明，NGC 5908的暗物质晕质量为$M_{\rm vir}\sim10^{13}\rm~M_{\rm \odot}$，使其成为最大质量的孤立螺旋星系之一。$^{12}$ CO/ $^{13}$ CO $J=1-0$、$^{12}$ CO $J=2-1$ / $J=1-0$的线比和估计的分子气体温度都表明在这个相当富含气体的大质量孤立螺旋星系中有正常但不可忽略的恒星形成，与测量的恒星形成强度和表面密度一致。该星系可能处于早期演化阶段，经过合并和/或星爆的快速增长阶段，有大量剩余的冷气体，相对较高的SFR，低的热CGM冷却速率和低的X射线发射率。
Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097
NGC 1097是附近的一个棒旋星系，据信正在与位于其西北部的椭圆星系NGC 1097 A相互作用。它拥有一个塞弗特1核，周围环绕着一个星暴环。两条笔直的尘埃带连接到环上，几乎连续不断地延伸到酒吧。尘埃带的另一端连接到两个主旋臂上。为了对其结构和运动学特性提供物理理解，进行了二维流体动力学模拟。数值计算表明，气体的形态和运动学的许多功能可以重现提供的气体流量是由一个缓慢旋转的强酒吧相关的重力势。在计算中考虑了气体盘的自引力，我们发现星暴环是引力不稳定的，这与\citet{hsieh11}的观测结果是一致的。我们的模拟表明，气体流入率为0.17 M $_\sun$年$^{-1}$到该地区内的星暴环，即使在其形成后，导致核环和环核盘的共存。
