X-raying the galaxy pair Arp 41: no collision in NGC 1232 and three ultraluminous sources in NGC 1232A

ABSTRACT We studied the apparent galaxy pair NGC 1232/NGC 1232A with Chandra, looking for evidence of interactions and collisions. We report that there is no cloud of diffuse emission in NGC 1232, contrary to previous claims in the literature. Instead, we find that the small ‘companion’ galaxy NGC 1232A contains three ultraluminous X-ray sources with peak 0.3–10 keV luminosities above 1040 erg s−1 (assuming a cosmological distance of ≈93 Mpc for this galaxy). For its mass, morphology, metal abundance, and bright ULX population, NGC 1232A is analogous to the more nearby late-type spiral NGC 1313.

Distance measures in cosmology: a simple approach

The aim of this paper is to analyze the concept of cosmological distance with a simple didactic approach that is not easy to find in textbooks. In this way, we hope to help facilitate student learning about this issue.

Cosmological distances scale: Part 10. The global Anisotropy

A brief overview of the history of the origin and development of the cosmological distance scale based on redshift is given. Statistical aspects of the problem of calibration of scales of this type are considered and their analogy with the problems of calibration of measurement tools is shown. The analysis of the first data on the basis of which the “accelerated expansion of the Universe” was detected. The Consequences of Anisotropy for Distance Scale is analyzed.

Cosmological distances scale. Pt. 12. Confluence analysis, rang inversion and tests for inadequacy

The measurement problem of calibration of the cosmological distance scale is considered from the point of view of the conditions of applicability of the regression analysis. It is shown that the rank inversion and statistical heterogeneity of data on supernovae SN Ia, which were used in 1998–1999 to detect the “acceleration of the expansion of the Universe”, and in 2004–2007 – as “extraordinary evidence” of its existence, is the reason for the discrepancy and inconsistency of the obtained estimates of the parameters of the Friedman-Robertson-Walker model. Although the use of tests for inadequacy for models of the cosmological distance scale reduces these negative effects, the fact remains that the cosmological distance scale based on redshift has neither the status of metric nor ordinal.

Cosmological distances scale: Pt. 11. Extraordinary evidences and cosmically jerk problem

Statistical verification of the “extraordinary” evidence of “acceleration of the expansion of the Universe” due to the “cosmic push” at the redshift interval and at based on data on supernovae of type SN Ia, for which photometric distances were determined, was carried out. The transition from “deceleration” to “acceleration” is considered as a “breakdown” – a change in the structure and parameters of the model of the cosmological distance scale. It is shown that data from different sources do not form a compositionally homogeneous set. The scale model's “misalignment” (discord) was revealed for from a sample of 10 SN Ia obtained in the interval by the High-Z Supernovae Search Team, and for from a sample of 42 SN Ia obtained in the interval by the Supernovae Cosmology Project group. The reason for these “discrepancies” may be an unbalanced and random distribution of SN Ia over the observed range of redshifts with a clearly expressed non-metric character of the scale.

Forecasting cosmological bias due to local gravitational redshift

When photons from distant galaxies and stars pass through our neighboring environment, the wavelengths of the photons would be shifted by our local gravitational potential. This local gravitational redshift effect can potentially have an impact on the measurement of cosmological distance–redshift relation. Using available supernovae data, Wojtak, Davis and Wiis [J. Cosmol. Astropart. Phys. 2015 (2015) 025] found seemingly large biases of cosmological parameters for some extended models (nonflat [Formula: see text]CDM, [Formula: see text]CDM, etc.). Huang [Phys. Rev. D 91 (2015) 121301] pointed out that, however, the biases can be reduced to a negligible level if cosmic microwave background (CMB) data are added to break the strong degeneracy between parameters in the extended models. In this paper, we forecast the cosmological bias due to local gravitational redshifts for a future WFIRST-like supernovae survey. We find that the local gravitational redshift effect remains negligible, provided that CMB data or some future redshift survey data are added to break the degeneracy between parameters.