Hunting Dark Matter Lines in the Infrared Background with the James Webb Space Telescope

Dark matter particles with a mass around 1 eV can decay into near-infrared photons. Utilising available public blank sky observations from the NIRSpec IFU on the James Webb Space Telescope (JWST), we search for a narrow emission line due to decaying dark matter and derive leading constraints in the mass range 0.8-3 eV on the decay rate to photons, and more specifically, on the axion-photon coupling for the case of axion-like particles. We exclude $\tau < 6.7\cdot 10^{26}$ s at $m_{\rm DM} \simeq 0.9$ eV and, in the case of axions, $g_{a \gamma \gamma} > 9.4 \cdot 10^{-12}$ GeV$^{-1}$ for $m_a = 2.15$ eV. Our results do not rely on dedicated observations, rather we use blank sky observations intended for sky subtraction, and thus our reach may be automatically strengthened as JWST continues to observe.Comment: 12 pages, 2 figure

An algorithm for rapid measurement of aberrations in pairs of out-of-focus images

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 57).In this thesis, I present a new technique for measuring the optical aberrations produced by a telescope, with an eye towards future use of these aberration measurements to align wide-field telescopes. This method determines the aberrations by simultaneously fitting a pair of oppositely defocused images to a mostly analytic model. I develop the model and describe its software implementation in detail, and then report on the results of tests with simulated and real data. This technique is able to extract the aberrations from simulated data rapidly and accurately, and it has been used with mixed success to analyze data from the VISTA telescope. With the VISTA data, the algorithm is unable to match small-scale brightness variations in the images. However, it was able to determine aberrations with median accuracies of 0.08 um for coma, 0.08 um for astigmatism, 0.9 um for tilt, and 0.3 um for defocus. It was also quite fast, with an average of 34 iterations until convergence.by Ryan J. Janish.S.B

The MASSIVE Survey - I. A Volume-Limited Integral-Field Spectroscopic Study of the Most Massive Early-Type Galaxies within 108 Mpc

Massive early-type galaxies represent the modern-day remnants of the earliest major star formation episodes in the history of the universe. These galaxies are central to our understanding of the evolution of cosmic structure, stellar populations, and supermassive black holes, but the details of their complex formation histories remain uncertain. To address this situation, we have initiated the MASSIVE Survey, a volume-limited, multi-wavelength, integral-field spectroscopic (IFS) and photometric survey of the structure and dynamics of the ~100 most massive early-type galaxies within a distance of 108 Mpc. This survey probes a stellar mass range M* > 10^{11.5} Msun and diverse galaxy environments that have not been systematically studied to date. Our wide-field IFS data cover about two effective radii of individual galaxies, and for a subset of them, we are acquiring additional IFS observations on sub-arcsecond scales with adaptive optics. We are also acquiring deep K-band imaging to trace the extended halos of the galaxies and measure accurate total magnitudes. Dynamical orbit modeling of the combined data will allow us to simultaneously determine the stellar, black hole, and dark matter halo masses. The primary goals of the project are to constrain the black hole scaling relations at high masses, investigate systematically the stellar initial mass function and dark matter distribution in massive galaxies, and probe the late-time assembly of ellipticals through stellar population and kinematical gradients. In this paper, we describe the MASSIVE sample selection, discuss the distinct demographics and structural and environmental properties of the selected galaxies, and provide an overview of our basic observational program, science goals and early survey results.Comment: 19 pages, 14 figures. ApJ (2014) vol. 795, in pres

The MASSIVE Survey II: Stellar Population Trends Out to Large Radius in Massive Early Type Galaxies

We examine stellar population gradients in ~100 massive early type galaxies spanning 180 < sigma* < 370 km/s and M_K of -22.5 to -26.5 mag, observed as part of the MASSIVE survey (Ma et al. 2014). Using integral-field spectroscopy from the Mitchell Spectrograph on the 2.7m telescope at McDonald Observatory, we create stacked spectra as a function of radius for galaxies binned by their stellar velocity dispersion, stellar mass, and group richness. With excellent sampling at the highest stellar mass, we examine radial trends in stellar population properties extending to beyond twice the effective radius (~2.5 R_e). Specifically, we examine trends in age, metallicity, and abundance ratios of Mg, C, N, and Ca, and discuss the implications for star formation histories and elemental yields. At a fixed physical radius of 3-6 kpc (the likely size of the galaxy cores formed at high redshift) stellar age and [alpha/Fe] increase with increasing sigma* and depend only weakly on stellar mass, as we might expect if denser galaxies form their central cores earlier and faster. If we instead focus on 1-1.5 R_e, the trends in abundance and abundance ratio are washed out, as might be expected if the stars at large radius were accreted by smaller galaxies. Finally, we show that when controlling for \sigmastar, there are only very subtle differences in stellar population properties or gradients as a function of group richness; even at large radius internal properties matter more than environment in determining star formation history.Comment: 17 pages, 9 figures, accepted by ApJ; resubmitted with updated reference

The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies

We present spatially-resolved two-dimensional stellar kinematics for the 41 most massive early-type galaxies (MK ~ 10^11.8 Msun) of the volume-limited (D < 108 Mpc) MASSIVE survey. For each galaxy, we obtain high-quality spectra in the wavelength range of 3650 to 5850 A from the 246-fiber Mitchell integral-field spectrograph (IFS) at McDonald Observatory, covering a 107" x 107" field of view (often reaching 2 to 3 effective radii). We measure the 2-D spatial distribution of each galaxy's angular momentum (lambda and fast or slow rotator status), velocity dispersion (sigma), and higher-order non-Gaussian velocity features (Gauss-Hermite moments h3 to h6). Our sample contains a high fraction (~80% ) of slow and non-rotators with lambda <~ 0.2. When combined with the lower-mass ETGs in the ATLAS3D survey, we find the fraction of slow-rotators to increase dramatically with galaxy mass, reaching ~50% at MK ~ -25.5 mag and ~90% at MK <~ -26 mag. All of our fast rotators show a clear anti-correlation between h3 and V/sigma, and the slope of the anti-correlation is steeper in more round galaxies. The radial profiles of sigma show a clear luminosity and environmental dependence: the 12 most luminous galaxies in our sample (MK <~ -26 mag) are all brightest cluster/group galaxies (except NGC 4874) and all have rising or nearly flat sigma profiles, whereas five of the seven "isolated" galaxies are all fainter than MK = -25.8 mag and have falling sigma. All of our galaxies have positive average h4; the most luminous galaxies have average h4 ~ 0.05 while less luminous galaxies have a range of values between 0 and 0.05. Most of our galaxies show positive radial gradients in h4, and those galaxies also tend to have rising sigma profiles. We discuss the implications for the relationship among dynamical mass, sigma, h4, and velocity anisotropy for these massive galaxies.Comment: 32 pages, 14 figures, 16 appendix figures. Accepted to MNRA

Supernovae as Dark Matter Signals

The empirical study of ultraheavy dark matter (DM) requires astrophysical probes. We present here a detailed study of DM-induced type Ia supernovae as one such probe. Dark matter may heat a small region in a white dwarf (WD) sufficient to trigger runaway fusion and ignite a supernova. We consider DM candidates that heat through the production of high-energy standard model (SM) particles, and show that such particles efficiently thermalize the WD medium and ignite supernovae. Based on the existence of long-lived WDs and the observed supernovae rate, we put new constraints on ultra-heavy DM candidates with masses above 10^{16} GeV that produce SM particles through annihilation, decay, and DM-SM scattering in the stellar medium. As a concrete example, this rules out supersymmetric Q-ball DM in parameter space complementary to terrestrial bounds. We further consider the possibility of DM capture by WDs, leading to the formation and self-gravitational collapse of a DM core within the star. This process allows two additional mechanisms for DM-induced particle heating, which we study here. For asymmetric DM, such a core may form a black hole that ignites a supernovae via Hawking radiation. For DM with a sufficiently small but nonzero annihilation cross section the core may cause ignition via a burst of annihilation during gravitational collapse. These processes are sensitive to much less massive candidates, down to 10^7 GeV, than are the mechanisms involving a single DM particle. It is also intriguing that these DM-induced ignition scenarios provide an alternative mechanism of triggering supernovae from sub-Chandrasekhar mass progenitors

Supernovae as Dark Matter Signals

The empirical study of ultraheavy dark matter (DM) requires astrophysical probes. We present here a detailed study of DM-induced type Ia supernovae as one such probe. Dark matter may heat a small region in a white dwarf (WD) sufficient to trigger runaway fusion and ignite a supernova. We consider DM candidates that heat through the production of high-energy standard model (SM) particles, and show that such particles efficiently thermalize the WD medium and ignite supernovae. Based on the existence of long-lived WDs and the observed supernovae rate, we put new constraints on ultra-heavy DM candidates with masses above 10^{16} GeV that produce SM particles through annihilation, decay, and DM-SM scattering in the stellar medium. As a concrete example, this rules out supersymmetric Q-ball DM in parameter space complementary to terrestrial bounds. We further consider the possibility of DM capture by WDs, leading to the formation and self-gravitational collapse of a DM core within the star. This process allows two additional mechanisms for DM-induced particle heating, which we study here. For asymmetric DM, such a core may form a black hole that ignites a supernovae via Hawking radiation. For DM with a sufficiently small but nonzero annihilation cross section the core may cause ignition via a burst of annihilation during gravitational collapse. These processes are sensitive to much less massive candidates, down to 10^7 GeV, than are the mechanisms involving a single DM particle. It is also intriguing that these DM-induced ignition scenarios provide an alternative mechanism of triggering supernovae from sub-Chandrasekhar mass progenitors