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arXiv 1306.2420astro-ph.GA
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恒星形成影响中性ISM的时间尺度

Timescales on which Star Formation Affects the Neutral ISM

Adrienne M. Stilp, Julianne J. Dalcanton, Steven R. Warren, Daniel R. Weisz, Evan Skillman, Juergen Ott, Benjamin F. Williams, Andrew E. Dolphin

摘要:

湍流中性氢(HI)谱线宽度通常被认为主要是由恒星形成(SF)驱动的,但SF能量转化为HI动能的时间尺度尚不清楚。作为一个复杂的,在外部星系的Hi线宽和SF之间的连接的研究往往使用宽带示踪剂的SF率,这必须隐含地假设SF的历史(SFHs)一直是恒定的时间尺度的示踪剂。在本文中,我们比较了HI能量的措施,时间分辨SFH在一些附近的矮星系。我们发现HI能量面密度仅与30-40百万年前发生的SF密切相关。这个时间尺度对应于最低质量超新星祖先(~ 8 Msun)的近似寿命。这一分析表明,SF和中性ISM之间的耦合是最强的,在这个时间尺度上,由于从SF的峰值能量的释放之间的固有延迟或在此期间的许多SNe的相干效应。在3000万年~ 4000万年的时间尺度上,当SFR > 10^-3 Msun yr^-1 kpc^-2时,我们发现SF能和HI能之间的平均耦合效率为ε= 0.11 +/- 0.04。然而,在较低的超导磁共振频率下系统需要非物理效率,这意味着在超导磁共振频率< 10^-3 Msun yr^-1 kpc^-2的情况下,超导磁共振频率并不是高电离层运动学的主要驱动因素。

英文摘要:

Turbulent neutral hydrogen (HI) line widths are often thought to be driven primarily by star formation (SF), but the timescale for converting SF energy to HI kinetic energy is unclear. As a complication, studies on the connection between Hi line widths and SF in external galaxies often use broadband tracers for the SF rate, which must implicitly assume that SF histories (SFHs) have been constant over the timescale of the tracer. In this paper, we compare measures of HI energy to time-resolved SFHs in a number of nearby dwarf galaxies. We find that HI energy surface density is strongly correlated only with SF that occurred 30-40 Myr ago. This timescale corresponds to the approximate lifetime of the lowest mass supernova progenitors (~ 8 Msun). This analysis suggests that the coupling between SF and the neutral ISM is strongest on this timescale, due either to an intrinsic delay between the release of the peak energy from SF or to the coherent effects of many SNe during this interval. At Σ_SFR > 10^-3 Msun yr^-1 kpc^-2, we find a mean coupling efficiency between SF energy and HI energy of ε= 0.11 +/- 0.04 using the 30-40 Myr timescale. However, unphysical efficiencies are required in lower Σ_SFR systems, implying that SF is not the primary driver of HI kinematics at Σ_SFR < 10^-3 Msun yr^-1 kpc^-2.

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