分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We propose a novel set of Poisson Cluster Process models to detect Ultra-Diffuse Galaxies (UDGs), a recently-discovered class of galaxies that are challenging to detect and are of substantial interests in modern astrophysics. We construct an improved spatial birth-death-move MCMC algorithm to make inferences about the locations of these otherwise un-observable galaxies. Our novel models significantly out-perform existing approaches based on the Log-Gaussian Cox Process; the novel marked point process we propose can also improve the detection performance for UDGs in noisy environments. We find evidence of a potential new "dark galaxy" that was not detected using previous methods.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Amanda M. Cook
Mohit Bhardwaj
B. M. Gaensler
Paul Scholz
Gwendolyn M. Eadie
Alex S. Hill
Victoria M. Kaspi
Kiyoshi W. Masui
Alice P. Curtin
Fengqiu Adam Dong
Emmanuel Fonseca
Antonio Herrera-Martin
Jane Kaczmarek
Adam E. Lanman
Mattias Lazda
Calvin Leung
Bradley W. Meyers
Daniele Michilli
Ayush Pandhi
Aaron B. Pearlman
摘要： The CHIME/FRB project has detected hundreds of fast radio bursts (FRBs), providing an unparalleled population to probe statistically the foreground media that they illuminate. One such foreground medium is the ionized halo of the Milky Way (MW). We estimate the total Galactic electron column density from FRB dispersion measures (DMs) as a function of Galactic latitude using four different estimators, including ones that assume spherical symmetry of the ionized MW halo and ones that imply more latitudinal-variation in density. Our observation-based constraints of the total Galactic DM contribution for $|b|\geq 30^\circ$, depending on the Galactic latitude and selected model, span 87.8 - 141 pc cm^-3. This constraint implies upper limits on the MW halo DM contribution that range over 52-111 pc cm^-3. We discuss the viability of various gas density profiles for the MW halo that have been used to estimate the halo's contribution to DMs of extragalactic sources. Several models overestimate the DM contribution, especially when assuming higher halo gas masses (~ 3.5 x 10^12 solar masses). Some halo models predict a higher MW halo DM contribution than can be supported by our observations unless the effect of feedback is increased within them, highlighting the impact of feedback processes in galaxy formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Dayi Li
Gwendolyn M. Eadie
Roberto G. Abraham
Patrick E. Brown
William E. Harris
Steven R. Janssens
Aaron J. Romanowsky
Pieter van Dokkum
Shany Danieli
摘要： We introduce a new method for detecting ultra-diffuse galaxies by searching for over-densities in intergalactic globular cluster populations. Our approach is based on an application of the log-Gaussian Cox process, which is a commonly used model in the spatial statistics literature but rarely used in astronomy. This method is applied to the globular cluster data obtained from the PIPER survey, a \textit{Hubble Space Telescope} imaging program targeting the Perseus cluster. We successfully detect all confirmed ultra-diffuse galaxies with known globular cluster populations in the survey. We also identify a potential galaxy that has no detected diffuse stellar content. Preliminary analysis shows that it is unlikely to be merely an accidental clump of globular clusters or other objects. If confirmed, this system would be the first of its kind. Simulations are used to assess how the physical parameters of the globular cluster systems within ultra-diffuse galaxies affect their detectability using our method. We quantify the correlation of the detection probability with the total number of globular clusters in the galaxy and the anti-correlation with increasing half-number radius of the globular cluster system. The S\'{e}rsic index of the globular cluster distribution has little impact on detectability.
点击量
待评议
点击量
下载量
评论
