44 research outputs found
The Direct Detectability of Giant Exoplanets in the Optical
Motivated by the possibility that a coronagraph will be put on WFIRST/AFTA,
we explore the direct detectability of extrasolar giant planets (EGPs) in the
optical. We quantify a planet's detectability by the fraction of its orbit for
which it is in an observable configuration (). Using a suite of
Monte Carlo experiments, we study the dependence of upon the
inner working angle (IWA) and minimum achievable contrast () of
the direct-imaging observatory; the planet's phase function, geometric albedo,
single-scattering albedo, radius, and distance from Earth; and the semi-major
axis distribution of EGPs. We calculate phase functions for a given geometric
or single-scattering albedo, assuming various scattering mechanisms. We find
that the Lambertian phase function can predict significantly larger
's with respect to the more realistic Rayleigh phase function.
For observations made with WFIRST/AFTA's baseline capabilities
(, ), Jupiter-like planets
orbiting stars within 10, 30, and 50 parsecs of Earth have volume-averaged
observability fractions of 12%, 3%, and 0.5%, respectively. At 10
parsecs, such observations yield for low- to
modest-eccentricity planets with semi-major axes in the range
AU. If , this range extends to AU. We find
that, in all but the most optimistic configurations, the probability for
detection in a blind search is low (). However, with orbital
parameter constraints from long-term radial-velocity campaigns and Gaia
astrometry, the tools we develop in this work can be used to determine both the
most promising systems to target and when to observe them.Comment: 16 pages, 16 figures. Accepted for publication in Ap
Discovery of a red backsplash galaxy candidate near M81
Understanding quenching mechanisms in low-mass galaxies is essential for
understanding galaxy evolution overall. In particular, isolated galaxies are
important tools to help disentangle the complex internal and external processes
that impact star formation. Comparisons between quenched field and satellite
galaxies in the low mass regime offer a substantial opportunity for discovery,
although very few quenched galaxies with masses below are known outside the virial radius, , of any host halo.
Importantly, simulations and observations suggest that an in-between population
of backsplash galaxies also exists that may complement interpretations of
environmental quenching. Backsplash galaxies -- like field galaxies -- reside
outside the virial radius of a host halo, but their star formation can be
deeply impacted by previous interactions with more massive systems. In this
paper, we report the discovery of a low-mass () quenched galaxy approximately in projection from the
M81 group. We use surface brightness fluctuations (SBF) to investigate the
possibility that the new galaxy, dubbed dw0910p7326 (nicknamed Blobby), is a
backsplash galaxy or a more distant field galaxy. The measured SBF distance of
Mpc indicates that Blobby likely
lies between outside the combined M81--M82 system.
Given its distance and quiescence, Blobby is a good candidate for a backsplash
galaxy and could provide hints about the formation and evolution of these
interesting objects.Comment: 15 pages, 8 figures, to be submitted to MNRAS, comments welcome