Aghanim, N., Akrami, Y., Ashdown, M., Aumont, J., Baccigalupi, C., Ballardini, M., Banday, A. J., Barreiro, R. B., Bartolo, N., Basak, S., Benabed, K., Bersanelli, M., Bielewicz, P., Bonaldi, A., Bonavera, L., Bond, J. R., Borrill, J., Bouchet, F. R., Burigana, C., Calabrese, Erminia, Cardoso, J.F., Challinor, A., Chiang, H. C., Colombo, L. P. L., Combet, C., Crill, B. P., Curto, A., Cuttaia, F., de Bernardis, P., de Rosa, A., de Zotti, G., Delabrouille, J., Di Valentino, E., Dickinson, C., Diego, J. M., Doré, O., Ducout, A., Dupac, X., Dusini, S., Efstathiou, G., Elsner, F., Enßlin, T. A., Eriksen, H. K., Fantaye, Y., Finelli, F., Forastieri, F., Frailis, M., Franceschi, E., Frolov, A., Galeotta, S., Galli, S., Ganga, K., GénovaSantos, R. T., Gerbino, M., GonzálezNuevo, J., Górski, K. M., Gratton, S., Gruppuso, A., Gudmundsson, J. E., Herranz, D., Hivon, E., Huang, Z., Jaffe, A. H., Jones, W. C., Keihänen, E., Keskitalo, R., Kiiveri, K., Kim, J., Kisner, T. S., Knox, L., Krachmalnicoff, N., Kunz, M., KurkiSuonio, H., Lagache, G., Lamarre, J.M., Lasenby, A., Lattanzi, M., Lawrence, C. R., Le Jeune, M., Levrier, F., Lewis, A., Liguori, M., Lilje, P. B., Lilley, M., Lindholm, V., LópezCaniego, M., Lubin, P. M., Ma, Y.Z., MacíasPérez, J. F., Maggio, G., Maino, D., Mandolesi, N., Mangilli, A., Maris, M., Martin, P. G., MartínezGonzález, E., Matarrese, S., Mauri, N., McEwen, J. D., Meinhold, P. R., Mennella, A., Migliaccio, M., Millea, M., MivilleDeschênes, M.A., Molinari, D., Moneti, A., Montier, L., Morgante, G., Moss, A., Narimani, A., Natoli, P., Oxborrow, C. A., Pagano, L., Paoletti, D., Partridge, B., Patanchon, G., Patrizii, L., Pettorino, V., Piacentini, F., Polastri, L., Polenta, G., Puget, J.L., Rachen, J. P., Racine, B., Reinecke, M., Remazeilles, M., Renzi, A., Rocha, G., Rossetti, M., Roudier, G., RubiñoMartín, J. A., RuizGranados, B., Salvati, L., Sandri, M., Savelainen, M., Scott, D., Sirignano, C., Sirri, G., Stanco, L., SuurUski, A.S., Tauber, J. A., Tavagnacco, D., Tenti, M., Toffolatti, L., Tomasi, M., Tristram, M., Trombetti, T., Valiviita, J., Van Tent, F., Vielva, P., Villa, F., Vittorio, N., Wandelt, B. D., Wehus, I. K., White, M., Zacchei, A. and Zonca, A. 2017. Planck intermediate results: LI. features in the cosmic microwave background temperature power spectrum and shifts in cosmological parameters. Astronomy and Astrophysics 607 , A95. 10.1051/00046361/201629504 

PDF
 Published Version
Download (1MB)  Preview 
Abstract
The six parameters of the standard ΛCDM model have bestfit values derived from the Planck temperature power spectrum that are shifted somewhat from the bestfit values derived from WMAP data. These shifts are driven by features in the Planck temperature power spectrum at angular scales that had never before been measured to cosmicvariance level precision. We have investigated these shifts to determine whether they are within the range of expectation and to understand their origin in the data. Taking our parameter set to be the optical depth of the reionized intergalactic medium τ, the baryon density ωb, the matter density ωm, the angular size of the sound horizon θ∗, the spectral index of the primordial power spectrum, ns, and Ase−2τ (where As is the amplitude of the primordial power spectrum), we have examined the change in bestfit values between a WMAPlike large angularscale data set (with multipole moment ` < 800 in the Planck temperature power spectrum) and an all angularscale data set (` < 2500 Planck temperature power spectrum), each with a prior on τ of 0.07 ± 0.02. We find that the shifts, in units of the 1σ expected dispersion for each parameter, are {∆τ, ∆Ase−2τ, ∆ns, ∆ωm, ∆ωb, ∆θ∗} = {−1.7, −2.2, 1.2, −2.0, 1.1, 0.9}, with a χ 2 value of 8.0. We find that this χ 2 value is exceeded in 15% of our simulated data sets, and that a parameter deviates by more than 2.2σ in 9% of simulated data sets, meaning that the shifts are not unusually large. Comparing ` < 800 instead to ` > 800, or splitting at a different multipole, yields similar results. We examined the ` < 800 model residuals in the ` > 800 power spectrum data and find that the features there that drive these shifts are a set of oscillations across a broad range of angular scales. Although they partly appear similar to the effects of enhanced gravitational lensing, the shifts in ΛCDM parameters that arise in response to these features correspond to model spectrum changes that are predominantly due to nonlensing effects; the only exception is τ, which, at fixed Ase−2τ, affects the ` > 800 temperature power spectrum solely through the associated change in As and the impact of that on the lensing potential power spectrum. We also ask, “what is it about the power spectrum at ` < 800 that leads to somewhat different bestfit parameters than come from the full `range?” We find that if we discard the data at ` < 30, where there is a roughly 2σ downward fluctuation in power relative to the model that best fits the full `range, the ` < 800 bestfit parameters shift significantly towards the ` < 2500 bestfit parameters. In contrast, including ` < 30, this previously noted “low`deficit” drives ns up and impacts parameters correlated with ns, such as ωm and H0. As expected, the ` < 30 data have a much greater impact on the ` < 800 best fit than on the ` < 2500 best fit. So although the shifts are not very significant, we find that they can be understood through the combined effects of an oscillatorylike set of high`residuals and the deficit in low`power, excursions consistent with sample variance that happen to map onto changes in cosmological parameters. Finally, we examine agreement between Planck T T data and two other CMB data sets, namely the Planck lensing reconstruction and the T T power spectrum measured by the South Pole Telescope, again finding a lack of convincing evidence of any significant deviations in parameters, suggesting that current CMB data sets give an internally consistent picture of the ΛCDM model.
Item Type:  Article 

Date Type:  Publication 
Status:  Published 
Schools:  Physics and Astronomy 
Subjects:  Q Science > QB Astronomy 
Publisher:  EDP Sciences 
ISSN:  00046361 
Date of First Compliant Deposit:  24 November 2017 
Date of Acceptance:  10 September 2017 
Last Modified:  29 Nov 2017 10:47 
URI:  http://orca.cf.ac.uk/id/eprint/107055 
Citation Data
Cited 38 times in Scopus. View in Scopus. Powered By Scopus® Data
Actions (repository staff only)
Edit Item 