arXiv subjects

Caroline Heneka

Publications and source records attributed to Caroline Heneka.

32 records · Page 2Linked to original sources

arXiv2022

Cosmology with one galaxy?

Galaxies can be characterized by many internal properties such as stellar mass, gas metallicity, and star-formation rate. We quantify the amount of cosmological and astrophysical information that the internal properties of individual galaxies and their host dark matter halos contain. We train neural networks using hundreds of thousands of galaxies from 2,000 state-of-the-art hydrodynamic simulations with different cosmologies and astrophysical models of the CAMELS project to perform likelihood-free inference on the value of the cosmological and astrophysical parameters. We find that knowing the internal properties of a single galaxy allow our models to infer the value of $Ω_{\rm m}$, at fixed $Ω_{\rm b}$, with a $\sim10\%$ precision, while no constraint can be placed on $σ_8$. Our results hold for any type of galaxy, central or satellite, massive or dwarf, at all considered redshifts, $z\leq3$, and they incorporate uncertainties in astrophysics as modeled in CAMELS. However, our models are not robust to changes in subgrid physics due to the large intrinsic differences the two considered models imprint on galaxy properties. We find that the stellar mass, stellar metallicity, and maximum circular velocity are among the most important galaxy properties to determine the value of $Ω_{\rm m}$. We believe that our results can be explained taking into account that changes in the value of $Ω_{\rm m}$, or potentially $Ω_{\rm b}/Ω_{\rm m}$, affect the dark matter content of galaxies. That effect leaves a distinct signature in galaxy properties to the one induced by galactic processes. Our results suggest that the low-dimensional manifold hosting galaxy properties provides a tight direct link between cosmology and astrophysics.

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arXiv2021

Optimal survey parameters: Ly$α$ and H$α$ intensity mapping for synergy with the 21cm signal during reionization

Intensity mapping of multiple emission lines is emerging as a new branch to astronomy, to probe both properties of ionizing sources and the medium between, in particular the intergalactic medium. For Epoch of Reionization (EoR) studies, both multi-line experiments and analysis methods are still in their infancy. Here we explore optimal survey parameters for Ly$α$ (and H$α$) intensity mapping up to high redshifts of reionization, and requirements for optimised synergy with 21cm experiments. We investigate line sensitivity, spectral resolution and detector pixel size requirements for optimal (high signal-to-noise) mission output. Power and cross-power spectra in a fiducial setup are derived, as are mock intensity maps. For line power spectrum measurements a cumulative signal-to-noise of O$\left(10^3 \right)$, and for respective cross-spectra with SKA 21cm observations of O$\left(10\right)$ to O$\left(10^2\right)$ are possible per redshift bin around the midpoint of reionization. These high signal-to-noise tomographic measurements are in reach for line sensitivities $>8\times 10^{-18}$erg$\,$s$^{-1}$sr$^{-1}$Hz$^{-1}$, spectral resolution $R>250$ and detector pixel sizes $<2\,$arcsec; all three requirements are met by the proposed Cosmic Dawn Intensity Mapper (CDIM). For CDIM similar S/N values are in reach for H$α$. Already the planned NASA mission SPHEREx will detect during the EoR Ly$α$ autopower and cross power with 21cm, for sensitivities better than $10^{-18}$erg$\,$s$^{-1}$sr$^{-1}$Hz$^{-1}$ in a moderate 21cm foreground scenario (better than $10^{-17}$erg$\,$s$^{-1}$sr$^{-1}$Hz$^{-1}$ in an optimistic scenario). We advocate for IR missions in flavor of CDIM for a leap in IM and finish by providing a cookbook for successful multi-line IM during the EoR.

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arXiv2020

Constraining coupled quintessence with the 21cm signal

The 21cm line probes the evolution of matter perturbations over a wide range of redshifts, from the dark ages down to the completion of reionization. Observing the 21cm cosmological signal will extend our understanding of the evolution of the Universe and it is thus important to investigate the predictions of different cosmological models. In this paper we focus on the prospect of constraining coupled quintessence models during the Epoch of Reionization both for global signal experiments and for intensity mapping surveys. To derive the all-sky 21cm signal and fluctuations in coupled quintessence, we simulate cosmological volumes of the 21cm signal including the coupling between dark matter and the quintessence field, where the strength of the coupling is labeled by the parameter $Q$. We show that the coupling between dark matter and quintessence modifies structure formation and expedites the process of reionization. For the upcoming 21cm line surveys like SKA and a fiducial global 21cm signal experiment, we perform a Fisher matrix analysis to constrain the coupling $Q$ and the dark matter density parameter $Ω_\mathrm{dm}$. The results indicate that SKA will be able to place a 68% upper limit $0.04$ to $|Q|$. At the same time, such a global 21cm detector provides a constraint on the dark matter density parameter $Ω_\mathrm{dm}$ around $ΔΩ_{\rm dm}\approx 0.005$, whereas SKA sets a quite weaker constraint around $ΔΩ_{\rm dm}\approx0.1$. These constraints are comparable to those already obtained from the cosmic microwave background, but explore an entirely different redshift range.

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arXiv2020

The spin-temperature dependence of the 21cm -- LAE cross-correlation

Cross-correlating 21cm with known cosmic signals will be invaluable proof of the cosmic origin of the first 21cm detections. As some of the widest fields available, comprising thousands of sources with reasonably known redshifts, narrow-band Lyman alpha emitter (LAE) surveys are an obvious choice for such cross-correlation. Here we revisit the 21cm -- LAE cross-correlation, relaxing the common assumption of reionization occurring in a pre-heated intergalactic medium (IGM). Using specifications from the Square Kilometre Array and the Subary Hyper Supreme-Cam, we present new forecasts of the 21cm -- LAE cross-correlation function at $z\sim7$. We sample a broad parameter space of the mean IGM neutral fraction and spin temperature, ($\bar{x}_{\rm{HI}}$, $\bar{T}_{\rm S}$). The sign of the cross-correlation roughly follows the sign of the 21cm signal: ionized regions which surround LAEs correspond to relative hot spots in the 21cm signal when the neutral IGM is colder than the CMB, and relative cold spots when the neutral IGM is hotter than the CMB. The amplitude of the cross-correlation function generally increases with increasing $\bar{x}_{\rm{HI}}$, following the increasing bias of the cosmic HII regions. As is the case for 21cm, the strongest cross signal occurs when the IGM is colder than the CMB, providing a large contrast between the neutral regions and the ionized regions which host LAEs. We also vary the topology of reionization and the epoch of X-ray heating. The cross-correlation during the first half of reionization is sensitive to these topologies, and could thus be used to constrain them.

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arXiv2019

Status of kinematic cosmology with SN Ia: JLA, Pantheon and future constraints with LSST

In this work we derive state-of-the-art model-independent constraints on cosmology from SN Ia by measuring purely kinematical $\left( q,j \right)$ model parameters (where $q$ and $j$ are related to the first and second derivative of the Hubble parameter). For the JLA compilation of SN Ia an agreement within 2$σ$ of $Λ$CDM expectations is found, where best-fitting kinematical parameters are $q=-0.66 \pm 0.11$ and $j=0.41 ^{+0.32}_{-0.33}$. With $q=-0.73 \pm 0.13$ and $j=0.76 ^{+0.41}_{-0.43}$ the Pantheon sample shows even better agreement with the $Λ$CDM expectation of $j=1$ than JLA, hinting at less systematics and/or a higher number of SN Ia alleviating tensions. For the future we predict the precision achievable with SN Ia from the LSST deep survey as $Δq \sim 0.05$ and $Δj \sim 0.1$, which is systematics-limited and could lead to detect both deviations from $Λ$CDM (in $j$) or current expansion rates measured (in $q$). In comparison, for standard cosmological parameters we get $ΔΩ_\mathrm{m}=0.01$ and $Δw=0.07$ for LSST. Given the high number of SN Ia expected for LSST, kinematical parameters in up to 500 sky regions, each with their own individual Hubble diagram, can be constrained. For each region an individual precision at the 10s of percent level is within reach at current systematics-levels, comparable to present-day full-sky surveys. This will determine anisotropy in cosmic expansion, or the dark energy dipole, at the 10s of percent level at 10s of degree scales.

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arXiv2019

Stress testing the dark energy equation of state imprint on supernova data

This work determines the degree to which a standard Lambda-CDM analysis based on type Ia supernovae can identify deviations from a cosmological constant in the form of a redshift-dependent dark energy equation of state w(z). We introduce and apply a novel random curve generator to simulate instances of w(z) from constraint families with increasing distinction from a cosmological constant. After producing a series of mock catalogs of binned type Ia supernovae corresponding to each w(z) curve, we perform a standard Lambda-CDM analysis to estimate the corresponding posterior densities of the absolute magnitude of type Ia supernovae, the present-day matter density, and the equation of state parameter. Using the Kullback-Leibler divergence between posterior densities as a difference measure, we demonstrate that a standard type Ia supernova cosmology analysis has limited sensitivity to extensive redshift dependencies of the dark energy equation of state. In addition, we report that larger redshift-dependent departures from a cosmological constant do not necessarily manifest easier-detectable incompatibilities with the Lambda-CDM model. Our results suggest that physics beyond the standard model may simply be hidden in plain sight.

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arXiv2019

Photometry of high-redshift blended galaxies using deep learning

The new generation of deep photometric surveys requires unprecedentedly precise shape and photometry measurements of billions of galaxies to achieve their main science goals. At such depths, one major limiting factor is the blending of galaxies due to line-of-sight projection, with an expected fraction of blended galaxies of up to 50%. Current deblending approaches are in most cases either too slow or not accurate enough to reach the level of requirements. This work explores the use of deep neural networks to estimate the photometry of blended pairs of galaxies in monochrome space images, similar to the ones that will be delivered by the Euclid space telescope. Using a clean sample of isolated galaxies from the CANDELS survey, we artificially blend them and train two different network models to recover the photometry of the two galaxies. We show that our approach can recover the original photometry of the galaxies before being blended with $\sim$7% accuracy without any human intervention and without any assumption on the galaxy shape. This represents an improvement of at least a factor of 4 compared to the classical SExtractor approach. We also show that forcing the network to simultaneously estimate a binary segmentation map results in a slightly improved photometry. All data products and codes will be made public to ease the comparison with other approaches on a common data set.

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arXiv2019

Tomography of the Cosmic Dawn and Reionization Eras with Multiple Tracers

The Cosmic Dawn and Reionization epochs remain a fundamental but challenging frontier of astrophysics and cosmology. We advocate a large-scale, multi-tracer approach to develop a comprehensive understanding of the physics that led to the formation and evolution of the first stars and galaxies. We highlight the line intensity mapping technique to trace the multi-phase reionization topology on large scales, and measure reionization history in detail. Besides 21cm, we advocate for Lya tomography mapping during the epoch of Wouthuysen-Field coupling as an additional probe of the cosmic dawn era.

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arXiv2019

CDIM: Cosmic Dawn Intensity Mapper Final Report

The Cosmic Dawn Intensity Mapper (CDIM) will transform our understanding of the era of reionization when the Universe formed the first stars and galaxies, and UV photons ionized the neutral medium. CDIM goes beyond the capabilities of upcoming facilities by carrying out wide area spectro-imaging surveys, providing redshifts of galaxies and quasars during reionization as well as spectral lines that carry crucial information on their physical properties. CDIM will make use of unprecedented sensitivity to surface brightness to measure the intensity fluctuations of reionization on large-scales to provide a valuable and complementary dataset to 21-cm experiments. The baseline mission concept is an 83-cm infrared telescope equipped with a focal plane of 24 \times 20482 detectors capable of R = 300 spectro-imaging observations over the wavelength range of 0.75 to 7.5 μm using Linear Variable Filters (LVFs). CDIM provides a large field of view of 7.8 deg2 allowing efficient wide area surveys, and instead of moving instrumental components, spectroscopic mapping is obtained through a shift-and-stare strategy through spacecraft operations. CDIM design and capabilities focus on the needs of detecting faint galaxies and quasars during reionization and intensity fluctuation measurements of key spectral lines, including Lyman-α and Hα radiation from the first stars and galaxies. The design is low risk, carries significant science and engineering margins, and makes use of technologies with high technical readiness level for space observations.

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arXiv2019

Cosmic Dawn and Reionization: Astrophysics in the Final Frontier

The cosmic dawn and epoch of reionization mark the time period in the universe when stars, galaxies, and blackhole seeds first formed and the intergalactic medium changed from neutral to an ionized one. Despite substantial progress with multi-wavelength observations, astrophysical process during this time period remain some of the least understood with large uncertainties on our existing models of galaxy, blackhole, and structure formation. This white paper outlines the current state of knowledge and anticipated scientific outcomes with ground and space-based astronomical facilities in the 2020s. We then propose a number of scientific goals and objectives for new facilities in late 2020s to mid 2030s that will lead to definitive measurements of key astrophysical processes in the epoch of reionization and cosmic dawn.

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arXiv2017

Cold dark energy constraints from the abundance of galaxy clusters

We constrain cold dark energy of negligible sound speed using galaxy cluster abundance observations. In contrast to standard quasi-homogeneous dark energy, negligible sound speed implies clustering of the dark energy fluid at all scales, allowing us to measure the effects of dark energy perturbations at cluster scales. We compare those models and set the stage for using non-linear information from semi-analytical modelling in cluster growth data analyses. For this, we recalibrate the halo mass function with non-linear characteristic quantities, the spherical collapse threshold and virial overdensity, that account for model and redshift dependent behaviours, as well as an additional mass contribution for cold dark energy. We present the first constraints from this cold dark matter plus cold dark energy mass function using our cluster abundance likelihood, which self-consistently accounts for selection effects, covariances and systematic uncertainties. We combine cluster growth data with CMB, SNe Ia and BAO data, and find a shift between cold versus quasi-homogeneous dark energy of up to $1σ$. We make a Fisher matrix forecast of constraints attainable with cluster growth data from the on-going Dark Energy Survey (DES). For DES, we predict $\sim$50$\%$ tighter constraints on $\left(Ω_\mathrm{m},w \right)$ for cold dark energy versus $w$CDM models, with the same free parameters. Overall, we show that cluster abundance analyses are sensitive to cold dark energy, an alternative, viable model that should be routinely investigated alongside the standard dark energy scenario.

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arXiv2017

Probing the Intergalactic Medium with Ly$\mathrmα$ and 21 cm Fluctuations

We study 21cm and Ly$\mathrmα$ fluctuations, as well as H$\mathrmα$, while distinguishing between Ly$\mathrmα$ emission of galactic, diffuse, and scattered intergalactic medium (IGM) origin. Cross-correlation information about the state of the IGM is obtained, testing neutral versus ionized medium cases with different tracers in a seminumerical simulation setup. In order to pave the way toward constraints on reionization history and modeling beyond power spectrum information, we explore parameter dependencies of the cross-power signal between 21$\,$cm and Ly$\mathrmα$, which displays a characteristic morphology and a turnover from negative to positive correlation at scales of a couple Mpc$^{-1}$. In a proof of concept for the extraction of further information on the state of the IGM using different tracers, we demonstrate the use of the 21$\,$cm and H$\mathrmα$ cross-correlation signal to determine the relative strength of galactic and IGM emission in Ly$\mathrmα$. We conclude by showing the detectability of the 21$\,$cm and Ly$\mathrmα$ cross-correlation signal over more than one decade in scale at high signal-to-noise ratio for upcoming probes like SKA and the proposed all-sky intensity mapping satellites SPHEREx and CDIM, while also including the Ly$\mathrmα$ damping tail and 21cm foreground avoidance in the modeling.

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arXiv2014

Searching for bias and correlations in a Bayesian way

A range of Bayesian tools has become widely used in cosmological data treatment and parameter inference (see Kunz, Bassett & Hlozek (2007), Trotta (2008), Amendola, Marra & Quartin (2013)). With increasingly big datasets and higher precision, tools that enable us to further enhance the accuracy of our measurements gain importance. Here we present an approach based on internal robustness, introduced in Amendola, Marra & Quartin (2013) and adopted in Heneka, Marra & Amendola (2014), to identify biased subsets of data and hidden correlation in a model independent way.

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arXiv2014

Extensive search for bias in SNIa data

The use of advanced statistical analysis tools is crucial in order to improve cosmological parameter estimates via removal of systematic errors and identification of previously unaccounted for cosmological signals. Here we demonstrate the application of a new fully-Bayesian method, the internal robustness formalism, to scan for systematics and new signals in the recent supernova Ia Union compilations. Our analysis is tailored to maximize chances of detecting the anomalous subsets by means of a variety of sorting algorithms. We analyse supernova Ia distance moduli for effects depending on angular separation, redshift, surveys and hemispherical directions. The data have proven to be robust within 2 sigma, giving an independent confirmation of successful removal of systematics-contaminated supernovae. Hints of new cosmology, as for example the anisotropies reported by Planck, do not seem to be reflected in the supernova Ia data.

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