Gregory M. Green, Hans-Walter Rix, Leon Tschesche, Douglas Finkbeiner, Catherine Zucker, Edward F. Schlafly, Jan Rybizki, Morgan Fouesneau, René Andrae, Joshua Speagle
备注：
30 pages, 13 figures. Revised version published in ApJ, including new Fig. 13
We develop a data-driven model to map stellar parameters (effective temperature, surface gravity and metallicity) accurately and precisely to broad-band stellar photometry. This model must, and does, simultaneously constrain the passband-specific dust reddening vector in the Milky Way. The model uses a neural network to learn the (de-reddened) absolute magnitude in one band and colors across many bands, given stellar parameters from spectroscopic surveys and parallax constraints from Gaia. To demonstrate the effectiveness of this approach, we train our model on a dataset with spectroscopic parameters from LAMOST, APOGEE and GALAH, Gaia parallaxes, and optical and near-infrared photometry from Gaia, Pan-STARRS~1, 2MASS and WISE. Testing the model on these datasets leads to an excellent fit and a precise - and by construction accurate - prediction of the color-magnitude diagrams in many bands. This flexible approach rigorously links spectroscopic and photometric surveys, and also results in an improved, stellar-temperature-dependent reddening vector. As such, it provides a simple and accurate method for predicting photometry in stellar evolutionary models. Our model will form a basis to infer stellar properties, distances and dust extinction from photometric data, which should be of great use in 3D mapping of the Milky Way. Our trained model may be obtained at https://doi.org/10.5281/zenodo.3902382.
The MaNGA Stellar Library (MaStar) is a large collection of high-quality empirical stellar spectra designed to cover all spectral types and ideal for use in the stellar population analysis of galaxies observed in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The library contains 59,266 spectra of 24,130 unique stars with spectral resolution $R\sim1800$ and covering a wavelength range of $3,622-10,354$ Å. In this work, we derive five physical parameters for each spectrum in the library: effective temperature ($T_{eff}$), surface gravity ($\log g$), metalicity ($[Fe/H]$…
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。
How elliptical galaxies form is a key question in observational cosmology. While the formation of massive ellipticals is strongly linked to mergers, the low mass (Mstar < 10^9.5 MSun) regime remains less well explored. In particular, studying elliptical populations when they are blue, and therefore rapidly building stellar mass, offers strong constraints on their formation. Here, we study 108 blue, low-mass ellipticals (which have a median stellar mass of 10^8.7 MSun) at z < 0.3 in the COSMOS field. Visual inspection of extremely deep optical HSC images indicates that less than 3 per cent of t…
Line-driven ablation of circumstellar discs: IV. The role of disc ablation in massive star formation and its contribution to the stellar upper mass limit
In addition to their low stellar densities, ultra-diffuse galaxies (UDGs) have a broad variety of dynamical mass-to-light ratios, ranging from dark matter (DM) dominated systems to objects nearly devoid of DM. To investigate the origin of this diversity, we develop a simple, semi-empirical model that predicts the structural evolution of galaxies, driven by feedback from massive star clusters, as a function of their departure from the mean SMHM relation. The model predicts that a galaxy located $\gtrsim 0.5$ dex above the mean relation at $M_{\rm halo}=10^{10}M_{\odot}$ will host a factor of $\…
ALESS--JWST: Dust-driven Morphologies and Hidden Stellar Mass in $z\sim3$ Sub-millimeter Galaxies
International Center for Radio Astronomy Research (ICRAR), The University of Western Australia（西澳大利亚大学国际射电天文研究中心）；International Space Center (ISC), The University of Western Australia（西澳大利亚大学国际太空中心）；Leiden Observatory, Leiden University（莱顿大学莱登天文台）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（杜伦大学物理系河外天文中心）；European Space Agency (ESA), ESA Office, Space Telescope Science Institute（欧洲空间局（ESA）欧洲空间局办公室太空望远镜科学研究所）；Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天文学与天体物理学研究学院）；Space Telescope Science Institute（太空望远镜科学研究所）
In recent years, several analytic models have demonstrated that simple assumptions about halo growth and feedback-regulated star formation can match the (limited) existing observational data on galaxies at z>6. By extending such models, we demonstrate that imposing a time delay on stellar feedback (as inevitably occurs in the case of supernova explosions) induces burstiness in small galaxies. Although supernova progenitors have short lifetimes (~5-30 Myr), the delay exceeds the dynamical time of galaxies at such high redshifts. As a result, star formation proceeds unimpeded by feedback for sev…
The condensation of baryons within a dark matter (DM) halo during galaxy formation should result in some contraction of the halo as the combined system settles into equilibrium. We quantify this effect on the cuspy primordial halos predicted by DM-only simulations for the baryon distributions observed in the galaxies of the SPARC database. We find that the DM halos of high surface brightness galaxies (with $Σ_{\rm eff}\gtrsim100$ $L_\odot$ pc$^{-2}$ at 3.6 $μ$m) experience strong contraction. Halos become more cuspy as a result of compression: the inner DM density slope increases with the bary…
We consider the dynamics of and emission from growing superbubbles in a stratified interstellar gaseous disc driven by energy release from supernovae explosions in stellar clusters with {masses $M_{cl}= 10^5-1.6\times 10^6~M_\odot$}. Supernovae are spread randomly within a sphere of $r_c=60$ pc, and inject energy episodically with a specific rate $1/130~M_\odot^{-1}$ proportional to the star formation rate (SFR) in the cluster. Models are run for several values of SFR in the range $0.01$ to $0.1~M_\odot$ yr$^{-1}$, with the corresponding average surface energy input rate $\sim 0.04-0.4$ erg cm…
The reservoir of molecular gas (H$_{\rm 2}$) represents the fuel for the star formation (SF) of a galaxy. Connecting the star formation rate (SFR) to the available H$_{\rm 2}$ is key to accurately model SF in cosmological simulations of galaxy formation. We investigate how modifying the underlying modelling of H$_{\rm 2}$ and the description of stellar feedback in low-metallicity environments (LMF, i.e. low-metallicity stellar feedback) in cosmological, zoomed-in simulations of a Milky Way-size halo influences the formation history of the forming, spiral galaxy and its final properties. We exp…
StAGE: Stellar Archaeology-driven Galaxy Evolution II. Binary Black Hole Mergers in Quiescent Galaxies and their Star-forming Progenitors
SISSA（斯issa国际高等研究院）；INFN-Trieste（意大利国家核物理研究所的里雅斯特分部）；IFPU（理论物理学前沿研究所）；INAF-IRA（意大利国家天体物理研究所都灵天文台）；Univ. Heidelberg（海德堡大学）；Univ. of Trento（特伦托大学）；INAF-OAR（意大利国家天体物理研究所阿斯科利山天文台）
