We present a new technique for the determination of the low-mass slope ($α_1$; $M_* < 0.5 M_{\odot}$) of the present day stellar mass function (PDMF) using the pixel space fitting of integrated light spectra. It can be used to constrain the initial mass function (IMF) of stellar systems with relaxation timescales exceeding the Hubble time and testing the IMF universality hypothesis. We provide two versions of the technique: (1) a fully unconstrained determination of the age, metallicity, and $α_1$ and (2) a constrained fitting by imposing the externally determined mass-to-light ratio of the stellar population. We have tested our approach by Monte-Carlo simulations using mock spectra and conclude that: (a) age, metallicity and $α_1$ can be precisely determined by applying the unconstrained version of the code to high signal-to-noise datasets (S/N=100, R=7000 yield $Δα_1 \approx 0.1$); (b) the $M/L$ constraint significantly improves the precision and reduces the degeneracies, however its systematic errors will cause biased $α_1$ estimates; (c) standard Lick indices cannot constrain the PDMF because they miss most of the mass function sensitive spectral features; (d) the $α_1$ determination remains unaffected by the high-mass IMF shape ($α_3$; $M_* \ge 1 M_{\odot}$) variation for stellar systems older than 8 Gyr, while the intermediate-mass IMF slope ($α_2$; $0.5 \le M_* < 1 M_{\odot}$) may introduce biases into the best-fitting $α_1$ values if it is different from the canonical value $α_2 = 2.3$. We analysed observed intermediate resolution spectra of ultracompact dwarf galaxies with our technique and demonstrated its applicability to real data.
paired: A Statistical Framework for Detecting Stellar Binarity with Gaia RVs. I. Sensitivity to Unresolved Binaries
University of Florida（佛罗里达大学）；Center for Computational Astrophysics, Flatiron Institute（纽约市立学院西蒙斯数据科学研究所计算天体物理中心）；School of Physics & Astronomy, Monash University（蒙纳士大学物理与天文学院）；Center of Excellence for Astrophysics in Three Dimensions (ASTRO-3D)（三维天体物理学卓越中心）
NBursts+phot: parametric recovery of galaxy star formation histories from the simultaneous fitting of spectra and broad-band spectral energy distributions
The Cannon: A data-driven approach to stellar label determination
新的光谱调查提供了一致的恒星参数和丰度（“恒星标签”）在银河系数十万颗恒星的承诺：这构成了一个艰巨的光谱建模挑战。在许多情况下，有一个参考天体的子集，其恒星标签是已知的高保真度。我们利用这一点与大炮，一个新的数据驱动的方法来确定恒星标签从光谱数据。Cannon通过在每个波长拟合一个灵活的模型，从参考星的“已知”标签中学习连续归一化光谱如何依赖于这些标签;然后，Cannon使用这个模型来推导剩余巡天星的标签。我们通过在19个星团中的542颗恒星上训练模型作为参考对象来说明大炮，Teff，log g和[Fe/H]作为标签，然后将其应用于APOGEE DR 10的56，000颗恒星的光谱。大炮非常准确。它的恒星标签与DR 10中提供的APOGEE管道（ASPCAP）标签的恒星相比很好，均方根差异基本上与所述的ASPCAP不确定度相同。除了参考标签，大炮没有使用恒星模型或任何线列表，但需要一组跨越标签空间的参考对象。Cannon在较低的信噪比下表现良好，因为即使在APOGEE观测时间的九分之一，它也能提供非常好的标签。我们讨论了大炮的局限性和未来的潜力，特别是，使不同的光谱调查到一个一致的规模的恒星标签。
