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We examine the internal consistency of the Planck 2015 cosmic microwave background (CMB) temperature anisotropy power spectrum. We show that tension exists between cosmological constant cold dark matter (

We examine the impact of baryon acoustic oscillation (BAO) scale measurements on the discrepancy between the value of the Hubble constant (H 0 ) inferred from the local distance ladder and from Planck cosmic microwave background (CMB) data. While the BAO data alone cannot constrain H 0 , we show that combining the latest BAO results with WMAP, Atacama Cosmology Telescope (ACT), or South Pole Telescope (SPT) CMB data produces values of H 0 that are 2.4 − 3.1σ lower than the distance ladder, independent of Planck, and that this downward pull was less apparent in some earlier analyses that used only angle-averaged BAO scale constraints rather than full anisotropic information. At the same time, the combination of BAO and CMB data also disfavors the lower values of H 0 preferred by the Planck high-multipole temperature power spectrum. Combining galaxy and Lyman-α forest (Lyα) BAO with a precise estimate of the primordial deuterium abundance produces H 0 = 66.98 ± 1.18 km s −1 Mpc −1 for the flat ΛCDM model. This value is completely independent of CMB anisotropy constraints and is 3.0σ lower than the latest distance ladder constraint, although 2.4σ tension also exists between the galaxy BAO and Lyα BAO. These results show that it is not possible to explain the H 0 disagreement solely with a systematic error specific to the Planck data. The fact that tensions remain even after the removal of any single data set makes this intriguing puzzle all the more challenging to resolve.

The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravitational-wave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low . Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of r = 0.01 and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, τ .Recently, the BICEP2 experiment announced the detection of B-mode polarization at of 40-200, 5 but it is unclear whether this signal is cosmological or Galactic in nature. These results have generated strong interest in complementary experiments and have highlighted the importance of multi-frequency observations for foreground subtraction. A measurement of B-modes in the CMB would constitute important evidence for inflation and a measurement of the energy scale at which inflation occured. The tensor-to-scalar ratios, r ≤ 0.1, being probed correspond to E ∼ 10 16 GeV, near grand-unified-theory (GUT) energy scales. The gravitational waves from inflation are our only probe of the physics at such enormous energies and at such early times, just 10 −35 seconds after the Big Bang. They would also provide the first firm evidence for the existence of quantum-gravitational effects. 6 Detecting primordial gravitational waves requires greater frequency coverage to definitively rule out Galactic foreground contamination, as well as a measurement of the B-mode signal over a wider range of angular scales to verify the full shape of the B-mode power spectrum.A number of experiments are searching for B-mode polarization. Notably, the Planck satellite has mapped the entire sky in nine frequency bands from 30 to 857 GHz, allowing measurement of CMB polarization over a broad range of angular scales with the ability to remove Galactic foreground contamination; however, it is yet to be seen whether Planck will have the ability to constrain this signal. In this paper we present the Cosmology Large Angular Scale Surveyor (CLASS), which is leading the effort to map the CMB polarization at large angular scales from the ground. CLASS will observe in four frequency bands centered on 38, 93, 148, and 217 GHz. CLASS is uniquely poised to measure inflationary gravitational waves through its ability to measure CMB polarization at the largest angular scales, a...

We analyse 2,015 mid-infrared (MIR) spectra of galaxies observed with Spitzer's Infrared Spectrograph, including objects with growing super-massive black holes and objects where most of the infrared emission originates from newly formed stars. We determine if and how accreting super-massive black holes at the centre of galaxies -known as active galactic nuclei (AGN) -heat and ionize their host galaxies' dust and molecular gas. We use four MIR diagnostics to estimate the contribution of the AGN to the total MIR emission. We refer to galaxies whose AGN contribute more than 50 per cent of the total MIR emission as AGNdominated. We compare the relative strengths of PAH emission features and find that PAH grains in AGN-dominated sources have a wider range of sizes and fractional ionizations than PAH grains in non-AGN dominated sources. We measure rotational transitions of H 2 and estimate H 2 excitation temperatures and masses for individual targets, H 2 excitation temperatures for spectra stacked by their AGN contribution to the MIR, and the H 2 excitation temperature distributions via a hierarchical Bayesian model. We find an average 200 K difference between the excitation temperatures of the H 2 S(5) and H 2 S(7) pure rotational molecular hydrogen transition pair in AGN-dominated versus non-AGN dominated galaxies. Our findings suggest that AGN impact the interstellar medium of their host galaxies.