Hoffman, Y., Nusser, A., Valade, A., Libeskind, N. I., Tully, R. B., 2021, Monthly Notices of the Royal Astronomical Society
, 505, 3 , 3380 Published: August 2021
Surveys of galaxy distances and radial peculiar velocities can be used to reconstruct the large-scale structure. Other than systematic errors in the zero-point calibration of the galaxy distances the main source of uncertainties of such data is errors on the distance moduli, assumed here to be Gaussian and thus turning into lognormal errors on distances and velocities. Naively treated, this leads to spurious nearby outflow and strong infall at larger distances. The lognormal bias is corrected here and tested against mock data extracted from a ΛCDM simulation, designed to statistically follow the grouped Cosmicflows-3 (CF3) data. Considering a subsample of data points, all of which have the same true distances or the same redshifts, the lognormal bias arises because the means of the distributions of observed distances and velocities are skewed off the means of the true distances and velocities. However, the medians are invariant under the lognormal transformation. This invariance allows the Gaussianization of the distances and velocities and the removal of the lognormal bias. This bias Gaussianization correction (BGc) algorithm is tested against mock CF3 catalogues. The test consists of a comparison of the BGc estimated with the simulated distances and velocities and of an examination of the Wiener filter reconstruction from the BGc data. Indeed, the BGc eliminates the lognormal bias. The estimation of Hubble's constant (H0) is also tested. The residual of the BGc-estimated H0 from the simulated values is $-0.6\pm 0.7{\, \rm km \ s^{-1}\, Mpc^{-1}}$, and is dominated by the cosmic variance. The BGc correction of the actual CF3 data yields $H_0=75.8\pm 1.1{\, \rm km \ s^{-1}\, Mpc^{-1}}$.
Libeskind, N. I., Carlesi, E., Grand, R. J. J., Khalatyan, A., Knebe, A., Pakmor, R., Pilipenko, S., Pawlowski, M. S., Sparre, M., Tempel, E., Wang, P., Courtois, H. M., Gottlöber, S., Hoffman, Y., Minchev, I., Pfrommer, C., Sorce, J. G., Springel, V., Steinmetz, M., Tully, R. B., Vogelsberger, M., Yepes, G., 2020, Monthly Notices of the Royal Astronomical Society
, 498, 2 , 2968 Published: October 2020
We present the HESTIA simulation suite: High-resolutions Environmental Simulations of The Immediate Area, a set of cosmological simulations of the Local Group. Initial conditions constrained by the observed peculiar velocity of nearby galaxies are employed to accurately simulate the local cosmography. Halo pairs that resemble the Local Group are found in low resolutions constrained, dark matter only simulations, and selected for higher resolution magneto hydrodynamic simulation using the AREPO code. Baryonic physics follows the AURIGA model of galaxy formation. The simulations contain a high-resolution region of 3-5 Mpc in radius from the Local Group mid-point embedded in the correct cosmographic landscape. Within this region, a simulated Local Group consisting of a Milky Way and Andromeda like galaxy forms, whose description is in excellent agreement with observations. The simulated Local Group galaxies resemble the Milky Way and Andromeda in terms of their halo mass, mass ratio, stellar disc mass, morphology separation, relative velocity, rotation curves, bulge-disc morphology, satellite galaxy stellar mass function, satellite radial distribution, and in some cases, the presence of a Magellanic cloud like object. Because these simulations properly model the Local Group in their cosmographic context, they provide a testing ground for questions where environment is thought to play an important role.
Ocvirk, P., Aubert, D., Sorce, J. G., Shapiro, P. R., Deparis, N., Dawoodbhoy, T., Lewis, J., Teyssier, R., Yepes, G., Gottlöber, S., Ahn, K., Iliev, I. T., Hoffman, Y., 2020, Monthly Notices of the Royal Astronomical Society
, 496, 4 , 4087 Published: August 2020
Cosmic Dawn II (CoDa II) is a new, fully coupled radiation-hydrodynamics simulation of cosmic reionization and galaxy formation and their mutual impact, to redshift z < 6. With 40963 particles and cells in a 94 Mpc box, it is large enough to model global reionization and its feedback on galaxy formation while resolving all haloes above 108 M⊙. Using the same hybrid CPU-GPU code RAMSES-CUDATON as CoDa I in Ocvirk et al. (2016), CoDa II modified and re-calibrated the subgrid star formation algorithm, making reionization end earlier, at z ≳ 6, thereby better matching the observations of intergalactic Lyman α opacity from quasar spectra and electron-scattering optical depth from cosmic microwave background fluctuations. CoDa II predicts a UV continuum luminosity function in good agreement with observations of high-z galaxies, especially at z = 6. As in CoDa I, reionization feedback suppresses star formation in haloes below ∼2 × 109 M⊙, though suppression here is less severe, a possible consequence of modifying the star formation algorithm. Suppression is environment dependent, occurring earlier (later) in overdense (underdense) regions, in response to their local reionization times. Using a constrained realization of lambda cold dark matter constructed from galaxy survey data to reproduce the large-scale structure and major objects of the present-day Local Universe, CoDa II serves to model both global and local reionization. In CoDa II, the Milky Way and M31 appear as individual islands of reionization, i.e. they were not reionized by the progenitor of the Virgo cluster, or by nearby groups, or by each other.
Velocity and density field reconstructions of the volume of the universe within 0.05c derived from the Cosmicflows-3 catalog of galaxy distances has revealed the presence of a filamentary structure extending across ∼0.11c. The structure, at a characteristic redshift of 12,000 km s-1, has a density peak coincident with the celestial South Pole. This structure, the largest contiguous feature in the local volume and comparable to the Sloan Great Wall at half the distance, is given the name the South Pole Wall.
Kourkchi, E., Courtois, H. M., Graziani, R., Hoffman, Y., Pomarède, D., Shaya, E. J., Tully, R. B., 2020, The Astronomical Journal
, 159, 2 , 67 Published: February 2020
Tools are provided at the Extragalactic Distance Database website which provide relationships between the distances and velocities of galaxies based on smoothed versions of the velocity fields derived by the Cosmicflows program.
