Search Publications
Heating and cooling of the neutral ISM in the NGC 4736 circumnuclear ring
Armus, L.; Smith, J. D.; Draine, B. T. +12 more
The manner in which gas accretes and orbits within circumnuclear rings has direct implications for the star formation process. In particular, gas may be compressed and shocked at the inflow points, resulting in bursts of star formation at these locations. Afterwards the gas and young stars move together through the ring. In addition, star formatio…
The Massive Star Population in M101. III. Spectra and Photometry of the Luminous and Variable Stars
Humphreys, Roberta M.; Grammer, Skyler H.; Gerke, Jill
We discuss moderate-resolution spectra, multicolor photometry, and light curves of 31 of the most luminous stars and variables in the giant spiral M101. The majority are intermediate A- to F-type supergiants. We present new photometry and light curves for three known “irregular blue variables,” V2, V4, and V9, and identify a new candidate. Their s…
HST/WFC3 Observations of an Off-nuclear Superbubble in Arp 220
Kewley, Lisa J.; Lu, Jessica R.; Heckman, Timothy M. +9 more
We present a high spatial resolution optical and infrared study of the circumnuclear region in Arp 220, a late-stage galaxy merger. Narrowband imaging using Hubble Space Telescope/WFC3 has resolved the previously observed peak in Hα+[N ii] emission into a bubble-shaped feature. This feature measures 1.″6 in diameter, or 600 pc, and is only 1″ nort…
Tracing the Metal-poor M31 Stellar Halo with Blue Horizontal Branch Stars
Bell, Eric F.; Williams, Benjamin F.; Gilbert, Karoline M. +8 more
We have analyzed new Hubble Space Telescope (HST)/Advanced Camera for Surveys and HST/WFC3 imaging in F475W and F814W of two previously unobserved fields along the M31 minor axis to confirm our previous constraints on the shape of M31's inner stellar halo. Both of these new data sets reach a depth of at least F814W <27 and clearly detect the bl…
Kinematic and thermal structure at the onset of high-mass star formation
Henning, Th.; Krause, O.; Beuther, H. +6 more
Context. Even though high-mass stars are crucial for understanding a diversity of processes within our galaxy and beyond, their formation and initial conditions are still poorly constrained.
Aims: We want to understand the kinematic and thermal properties of young massive gas clumps prior to and at the earliest evolutionary stages of high-mas…
Follow-up observations of X-ray emitting hot subdwarf stars: the He-rich sdO BD +37° 1977
Tiengo, A.; Mereghetti, S.; Esposito, P. +2 more
We report on the results of the first XMM-Newton satellite observation of the luminous and helium-rich O-type subdwarf BD +37° 1977 carried out in April 2014. X-ray emission is detected with a flux of about 4 × 10-14 erg cm-2 s-1 (0.2-1.5 keV), corresponding to a fX/fbol ratio ~ 10-7
How CMB and large-scale structure constrain chameleon interacting dark energy
Wong, Yvonne Y. Y.; Boriero, Daniel; Das, Subinoy
We explore a chameleon type of interacting dark matter-dark energy scenario in which a scalar field adiabatically traces the minimum of an effective potential sourced by the dark matter density. We discuss extensively the effect of this coupling on cosmological observables, especially the parameter degeneracies expected to arise between the model …
The Warm CO Gas along the UV-heated Outflow Cavity Walls: A Possible Interpretation for the Herschel/PACS CO Spectra of Embedded YSOs
Lee, Jeong-Eun; Bergin, Edwin A.; Lee, Seokho
A fraction of the mid-J (J = 14-13 to J = 24-23) CO emission detected by the Herschel/Photodetector Array Camera and Spectrometer observations of embedded young stellar objects (YSOs) has been attributed to the UV-heated outflow cavity walls. We have applied our newly developed self-consistent models of photon-dominated-region (PDR) and non-local-…
Which fundamental constants for cosmic microwave background and baryon-acoustic oscillation?
Rich, James
We use the three-scale framework of Hu et al. to show how the cosmic microwave background (CMB) anisotropy spectrum depends on the fundamental constants. As expected, the spectrum depends only on dimensionless combinations of the constants, and we emphasize the points that make this generally true for cosmological observables. Our analysis suggest…
HST/STIS Ultraviolet Spectroscopy of the Components of the Massive Triple Star δ Ori A
Corcoran, Michael F.; Gies, Douglas R.; Moffat, Anthony F. J. +4 more
The multiple star system of δ Orionis is one of the closest examples of a system containing a luminous O-type, bright giant star (component Aa1). It is often used as a spectral-type standard and has the highest observed X-ray flux of any hot-star binary. The main component Aa1 is orbited by two lower mass stars, faint Aa2 in a 5.7 day eclipsing bi…