Stellar Halos from the The Dragonfly Edge-on Galaxies Survey

Abstract

We present the primary results from the Dragonfly Edge-on Galaxies Survey, an exploration of the stellar halos of twelve nearby (d < 25 Mpc) edge-on disk galaxies with the Dragonfly Telephoto Array. The edge-on orientation of these galaxies allows their stellar halos to be explored with minimal obscuration by or confusion with the much brighter disk light. Galaxies in the sample span a range of stellar masses from 109.68 to 1010.88 M ⊙. We confirm that the wide range of stellar halo mass fractions previously seen for Milky Way–mass galaxies is also found among less massive spiral galaxies. The scatter in stellar halo mass fraction is large, but we do find a significant positive correlation between stellar halo mass fraction and total stellar mass when the former is measured beyond five half-mass radii. Reasonably good agreement is found with predictions from cosmological hydrodynamical simulations, although observed stellar halo fractions appear to be somewhat lower than expected from these simulations.

Distributed aperture telescopes and the Dragonfly Telephoto Array

“…Growing the array is done by simply bolting a new lens onto the array and plugging in network and power cables. discovered a surprising diversity in stellar halos around nearby massive galaxies 19,20 and an abundance of ultradiffuse galaxies (a term coined by our team) in the Coma cluster, 21 leading to numerous other investigations of ultra-diffuse systems. [22][23][24][25][26][27][28] Dragonfly discoveries have been followed up with the world's largest telescopes to reveal remarkable properties of galaxies, including systems with anomalously high dark matter abundances, 29 and galaxies with no dark matter at all.…”

“…This component of the wide-angle scatter is variable, 37 and our Dragonfly data shows quite clearly that this variability extends down to a timescale of minutes. It is possible to account for wide-angle PSF contamination via post-facto measurement and subsequent modelling 14,20,38 and we have developed software tools for this purpose. 17 Until the properties of the wide-angle PSF are better understood, real-time monitoring of the large-angle PSF is likely to be important for reliable measurement of low surface brightness features on angular scales of arcminutes and larger.…”

SKYSURF-4: Panchromatic Hubble Space Telescope All-Sky Surface-brightness Measurement Methods and Results

“…There are many potential sources for DL, including missing galaxies (Conselice et al 2016;Lauer et al 2021), the extended outskirts of galaxies (e.g., Gilhuly et al 2022;Li et al 2022), intrahalo light (Bernstein et al 1995;Rudick et al 2011;Mihos 2019), reionization (Santos et al 2002;Cooray et al 2004;Kashlinsky et al 2004;Madau & Silk 2005;Matsumoto et al 2011), underestimated ZL or DGL models (Kawara et al 2017;Korngut et al 2022), telescope glow (Carleton et al 2022), and earthshine (Caddy et al 2022), as well as more exotic sources such as dark matter particles (Maurer et al 2012;Gong et al 2016) or black holes (Yue et al 2013). See Windhorst et al (2022) for a detailed summary.…”

A Recipe for Unbiased Background Modeling in Deep Wide-field Astronomical Images

“…However, the payoff for investigations that meet these challenges is proving to be enormous. Examples of important extragalactic science papers based on low surface brightness observations include studies of nearby dwarf galaxies (e.g., McConnachie 2012; Bechtol et al 2015;Geha et al 2017;Read et al 2017;Danieli et al 2018;Muñoz et al 2018;Drlica-Wagner et al 2021;Carlsten et al 2022), ultra-diffuse galaxies (UDGs; e.g., Mihos et al 2015;van Dokkum et al 2015;Yagi et al 2016;van Dokkum et al 2018), and galaxy outskirts (e.g., Tal et al 2009;Merritt et al 2016;Zhang et al 2018;Gilhuly et al 2022;Li et al 2022). Nonextragalactic science cases also abound, including investigations of solar system objects (e.g., Verbiscer et al 2009), debris disks (e.g., Schneider et al 2014;Hom et al 2020), light echoes (e.g., Rest et al 2008;Ortiz et al 2010), and Galactic cirrus (e.g., Ienaka et al 2013;Miville-Deschênes et al 2016;Román et al 2020).…”