Reinventing the slide rule for redshifts: the case for logarithmic wavelength shift

Baldry, I. K.

doi:10.48550/arxiv.1812.05135

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…where ζ is the appropriate quantity to use when dealing with redshift measurements and errors (Baldry 2018). The initial estimate of the uncertainty (or the nominal error) is given by:…”

Section: Updated Methodologymentioning

confidence: 99%

The galaxy stellar mass function from CCSNe with improved photo-z techniques

Sedgwick¹,

Baldry²,

James³

et al. 2019

Preprint

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In Sedgwick et al. (2019) we introduced and utilised a method to combat surface brightness and mass biases in galaxy sample selection, using core-collapse supernovae (CCSNe) as pointers towards their host galaxies, in order to: (i) search for low-surface brightness galaxies (LSBGs); (ii) assess the contributions of galaxies at a given mass to the star-formation-rate density (SFRD); and (iii) infer from this, using estimates of specific star-formation (SF) rate, the form of the SF-galaxy stellar mass function (GSMF). A CCSN-selection of SF-galaxies allows a probe of the form of the SFRD and GSMF deep into the dwarf galaxy mass regime. In the present work, we give improved constraints on our estimates of the SFRD and star-forming GSMF, in light of improved photometric redshift estimates required for estimates of galaxy stellar mass. The results are consistent with a power-law increase to SF-galaxy number density down to our low stellar mass limit of ∼ 10 6.2 M . No deviation from the high-mass version of the surface brightness -mass relation is found in the dwarf mass regime. These findings imply no truncation to galaxy formation processes at least down to ∼ 10 6.2 M .

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“…where ζ is the appropriate quantity to use when dealing with redshift measurements and errors (Baldry 2018). The initial estimate of the uncertainty (or the nominal error) is given by:…”

Section: Updated Methodologymentioning

confidence: 99%

The galaxy stellar mass function from CCSNe with improved photo-z techniques

Sedgwick¹,

Baldry²,

James³

et al. 2019

Preprint

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“…Note that regardless of the accuracy of the Hubble law, v accurately represents the integral of the velocity differences along the line-of-sight, precisely in the case of fundamental observers. This is evident from the additive nature of terms in ζ or v (Baldry 2018).…”

Section: Appendix A: a Second-order Hubble Lawmentioning

confidence: 99%

“…This is more accurate for pure line-of-sight velocity and means that the peculiar velocity and cosmological terms, and frame corrections, are additive (Baldry 2018). A common misconception is to assume cz terms are additive.…”

Section: Appendix A: a Second-order Hubble Lawmentioning

confidence: 99%

The effects of peculiar velocities in SN Ia environments on the local $H_0$ measurement

Sedgwick,

Collins,

Baldry

et al. 2019

Preprint

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The discrepancy between estimates of the Hubble Constant (H 0 ) measured from local (z 0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities of standard candle distance indicators can systematically affect local H 0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z < 0.05 underdensity in the SGC-6dFGS region of 27 ± 2 %. However, no strong evidence for a 'Local Void' pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, ∆φ +− , which acts as a proxy for peculiar velocity (v pec ) by quantifying density gradients along a line-of-sight. ∆φ +− is found to correlate strongly with local H 0 estimates from Union 2.1 Type Ia SNe (0.02 < z < 0.04). Density structures on scales of ∼ 50 Mpc are found to correlate most strongly with H 0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Interpolating SNIa H 0 estimates to their ∆φ +− = 0 values, we can correct for the effects of density structure on the local H 0 estimates, even in the presence of biased peculiar velocities. For these particular observational data, we reveal a < 0.1km s −1 Mpc −1 difference in the sample mean estimate compared to the value uncorrected for peculiar velocities. Our best estimate is then 74.9 km s −1 Mpc −1 . Using the mock data, the systematic uncertainty from these peculiar velocity corrections is estimated to be 0.3 km s −1 Mpc −1 . The dominant source of uncertainty in our estimate instead relates to Cepheid-based calibrations of distance moduli (1.7 km s −1 Mpc −1 ) and SN photometry (0.7 km s −1 Mpc −1 ).

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“…2 reflects the logarithmically spaced scalefactors a that were chosen for the snapshots. Constant spacing in the logarithm of the scalefactor has desirable properties when considering galaxy populations and cosmology, see Baldry (2018). Since the differences between two scalefactors thus translate to approximately (exactly in Einstein-de-Sitter space) constant comoving distances, the power spectra amplitudes undergo approximately constant multiplicative shifts as time evolves, at least in the regime of linear structure formation.…”

Section: Inferred Power Spectramentioning

confidence: 99%

On the cosmic web elongation in fuzzy dark matter cosmologies: Effects on density profiles, shapes, and alignments of haloes

Dome

Fialkov

Mocz

et al. 2022

Monthly Notices of the Royal Astronomical Society

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The fuzzy dark matter (FDM) scenario has received increased attention in recent years due to the small-scale challenges of the vanilla Lambda cold dark matter (ΛCDM) cosmological model and the lack of any experimental evidence for any candidate particle. In this study, we use cosmological N-body simulations to investigate high-redshift dark matter halos and their responsiveness to an FDM-like power spectrum cutoff on small scales in the primordial density perturbations. We study halo density profiles, shapes and alignments in FDM-like cosmologies (the latter two for the first time) by providing fits and quantifying departures from ΛCDM as a function of the particle mass m. Compared to ΛCDM, the concentrations of FDM-like halos are lower, peaking at an m-dependent halo mass and thus breaking the approximate universality of density profiles in ΛCDM. The intermediate-to-major and minor-to-major shape parameter profiles are monotonically increasing with ellipsoidal radius in N-body simulations of ΛCDM. In FDM-like cosmologies, the monotonicity is broken, halos are more elongated around the virial radius than their ΛCDM counterparts and less elongated closer to the center. Finally, intrinsic alignment correlations, stemming from the deformation of initially spherically collapsing halos in an ambient gravitational tidal field, become stronger with decreasing m. At z ∼ 4, we find a 6.4σ-significance in the fractional differences between the isotropised linear alignment magnitudes Diso in the m = 10−22 eV model and ΛCDM. Such FDM-like imprints on the internal properties of virialised halos are expected to be strikingly visible in the high-z Universe.

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Reinventing the slide rule for redshifts: the case for logarithmic wavelength shift

Cited by 4 publications

References 7 publications

The galaxy stellar mass function from CCSNe with improved photo-z techniques

The galaxy stellar mass function from CCSNe with improved photo-z techniques

The effects of peculiar velocities in SN Ia environments on the local $H_0$ measurement

On the cosmic web elongation in fuzzy dark matter cosmologies: Effects on density profiles, shapes, and alignments of haloes

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