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28 March 2024 |
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Figuring Out Gas & Galaxies in Enzo (FOGGIE). III. The Mocky Way: Investigating Biases in Observing the Milky Way's Circumgalactic Medium | Yong Zheng
; Molly S. Peeples
; Brian W. O'Shea
; Raymond C. Simons
; Cassandra Lochhaas
; Lauren Corlies
; Jason Tumlinson
; | Date: |
21 Jan 2020 | Abstract: | The circumgalactic medium (CGM) of the Milky Way is mostly obscured by nearby
gas in position-velocity space due to the location and motion of observers
inside the Galaxy. While most studies on the Milky Way’s CGM to date focus on
easier-to-detect high-velocity gas ($|v_{
m LSR}|gtrsim100$ km s$^{-1}$), it
only partially represents the entire CGM, resulting in substantial biases. Here
we investigate four observational biases inherent in the studies of the Milky
Way’s CGM with mock observations on a Milky-Way analog from the FOGGIE
simulations. With a mock observer placed inside the simulated galaxy at
off-center locations consistent with that of the Sun, we find that: (i)
high-velocity-based studies could miss $sim$2/3 of the Milky Way’s CGM mass;
(ii) once we correct velocities from the local standard of rest to the galaxy’s
rest frame, gas infall rate ($dot{M}$) for cold gas observable in HI 21cm
emission is reduced from -0.25 M$_odot$ to -0.05 M$_odot$, while $dot{M}$
for gases at warmer phases are less affected; (iii) OVI and NV are likely to be
good UV tracers of the Milky Way’s outer CGM ($rgtrsim$15 kpc), whereas CIV
maybe less sensitive; (iv) because of the clumpiness and radial distribution of
CGM gas, the scatter in ionic column densities is a factor of 2 higher when the
CGM is observed from the inside-out versus from external views. Our work
highlights that observations of the Milky Way’s CGM, especially those using HI
emission and UV absorption lines, are highly biased because we reside inside
the Galaxy. We demonstrate that these biases can be quantified and calibrated
through synthetic observations with simulated Milky-Way analogs. | Source: | arXiv, 2001.7736 | Services: | Forum | Review | PDF | Favorites |
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