THE IMPACT OF THE GAS DISTRIBUTION ON THE DETERMINATION OF DYNAMICAL MASSES OF GALAXIES USING UNRESOLVED OBSERVATIONS
THE IMPACT OF THE GAS DISTRIBUTION ON THE DETERMINATION OF DYNAMICAL MASSES OF GALAXIES USING UNRESOLVED OBSERVATIONS
复制标题
气体分布对利用未解决的观测确定星系动态质量的影响
DOI：
10.1088/0004-6256/147/5/96
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
F. Walter
中科院分区：
文献类型：
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作者：
W. D. de Blok;F. Walter
动态质量 (Mdyn) 是任何星系的关键属性，但如果无法进行空间分辨测量，则 Mdyn 的确定并不简单。这种情况发生在局部宇宙的单碟 H i 观测中，但也经常出现在高红移观测中。高红移星系中的 Mdyn 测量通常是通过观测 CO 谱线（分子介质中最丰富的示踪剂）来获得的。尽管在大多数情况下，可以以合理的精度确定 CO 线宽，但在给定现有设施的情况下，测量发射区域的尺寸通常具有挑战性。我们展示了各种星系模型的积分光谱（“全局剖面”）如何取决于示踪气体的空间分布及其速度色散。我们证明示踪剂发射线的选择（例如，H i 追踪扩展的“平坦”发射与 CO 追踪更紧凑的“指数”发射）会显着影响全局轮廓的形状。特别是，在高（∼50 km s−1）速度色散的情况下，紧凑的示踪剂（例如CO）会产生类高斯（非双角）轮廓，这在高红移观测中确实经常看到。如果考虑示踪材料的不同分布（“平坦”与“指数”），这会导致 Mdyn 的测定结果显着不同。我们确定旋转曲线在哪些半径处达到与速度宽度相对应的旋转速度，并发现对于每个示踪剂，这种情况发生在明确定义的半径处：H i速度宽度通常源自∼5光学尺度长度，而CO速度宽度在∼2尺度长度处追踪旋转速度。我们还探索了其他分布，以考虑到高红移处的 CO 分布可能与低红移处的 CO 分布不同。我们的模型虽然不试图重现单个星系，但定义了可以与测量的速度宽度结合使用的特征半径，以便定义与假设的气体分布一致的动态质量。
Dynamical mass (Mdyn) is a key property of any galaxy, yet a determination of Mdyn is not straightforward if spatially resolved measurements are not available. This situation occurs in single-dish H i observations of the local universe, but also frequently in high-redshift observations. Mdyn measurements in high-redshift galaxies are commonly obtained through observations of the CO line, the most abundant tracer of the molecular medium. Even though in most cases the CO line width can be determined with reasonable accuracy, a measurement of the size of the emitting region is typically challenging given current facilities. We show how the integrated spectra (“global profiles”) of a variety of galaxy models depend on the spatial distribution of the tracer gas as well as its velocity dispersion. We demonstrate that the choice of tracer emission line (e.g., H i tracing extended, “flat,” emission versus CO tracing more compact, “exponential,” emission) significantly affects the shape of the global profiles. In particular, in the case of high (∼50 km s−1) velocity dispersions, compact tracers (such as CO) result in Gaussian-like (non-double-horned) profiles, as is indeed frequently seen in high-redshift observations. This leads to significantly different determinations of Mdyn if different distributions of the tracer material (“flat” versus “exponential”) are considered. We determine at which radii the rotation curve reaches the rotation velocity corresponding to the velocity width, and find that for each tracer this happens at a well-defined radius: H i velocity widths typically originate at ∼5 optical scale lengths, while CO velocity widths trace the rotation velocity at ∼2 scale lengths. We additionally explore other distributions to take into account that CO distributions at high redshift likely differ from those at low redshift. Our models, while not trying to reproduce individual galaxies, define characteristic radii that can be used in conjunction with the measured velocity widths in order to define dynamical masses consistent with the assumed gas distribution.
DOI：
10.1088/0004-637x/768/1/74
发表时间：
2012-11
期刊：
The Astrophysical Journal
影响因子：
--
作者：
L. Tacconi;R. Neri;R. Genzel;F. Combes;A. Bolatto;M. Cooper;S. Wuyts;F. Bournaud;A. Burkert-
通讯作者：
L. Tacconi;R. Neri;R. Genzel;F. Combes;A. Bolatto;M. Cooper;S. Wuyts;F. Bournaud;A. Burkert-