Cosmology

Abstract:

The Large Scale Polarization Explorer (LSPE) project, funded by the Italian Space Agency (ASI), includes the development of LSPE-Strip, a ground-based radio telescope for observing Cosmic Microwave Background (CMB) anisotropies. LSPE-Strip, nearing its construction phase, will operate from the Teide Observatory in Tenerife, employing 49 coherent polarimeters at 43 GHz to deliver critical data on CMB anisotropies and 6 channels at 95 GHz as atmospheric monitor. On-site characterization of such advanced instruments is crucial to detect possible systematic effects, such as gain fluctuations, beam distortions, and pointing errors, that can compromise performance by introducing spurious polarizations or radiation collection from unintended directions. To address these challenges, a drone-mounted Q-band test source for on-site characterization of LSPE-Strip's polarimeter array was developed. Modern Unmanned Aerial Vehicles (UAVs) offer a flexible approach for antenna pattern measurements, yet their use in high-frequency radio astronomy is not consolidated practice. In October 2022, a UAV-based measurement campaign was conducted with the TFGI instrument on the second QUIJOTE telescope in Tenerife, in collaboration with the Instituto de Astrofísica de Canarias. This pioneering effort aimed to validate UAV-based beam characterization methods and assess QUIJOTE's performance under operational conditions. Preliminary results demonstrated high measurement accuracy, leveraging QUIJOTE's dual-receiver configuration for beam validation. These findings provide valuable insights for optimizing UAV systems in preparation for LSPE-Strip's future characterization.

Abstract:

Abstract We present the first results of the JWST Emission Line Survey (JELS). Utilising the first NIRCam narrow-band imaging at 4.7μm, over 63 arcmin2 in the PRIMER/COSMOS field, we have identified 609 emission line galaxy candidates. From these, we robustly selected 35 Hα star-forming galaxies at z ∼ 6.1, with Hα star-formation rates ($\rm {SFR_{H\alpha }}$) of $\sim 0.9-15\ \rm {{\rm M}_{\odot } \ yr^{-1}}$. Combining our unique Hα sample with the exquisite panchromatic data in the field, we explored their physical properties and star-formation histories, and compared these to a broad-band selected sample at z ∼ 6 which has offered vital new insights into the nature of high-redshift galaxies. UV-continuum slopes (β) were considerably redder for our Hα sample (〈β〉 ∼ −1.92) compared to the broad-band sample (〈β〉 ∼ −2.35). This was not due to dust attenuation as our Hα sample was relatively dust-poor (median AV = 0.23); instead, we argue that the reddened slopes could be due to nebular continuum. We compared $\rm {SFR_{H\alpha }}$ and the UV-continuum-derived $\rm {SFR_{UV}}$ to SED-fitted measurements averaged over canonical timescales of 10 and 100 Myr ($\rm {SFR_{10}}$ and $\rm {SFR_{100}}$). We found an increase in recent SFR for our sample of Hα emitters, particularly at lower stellar masses ($<10^9 \ \rm {{\rm M}_{\odot }}$). We also found that $\rm {SFR_{H\alpha }}$ strongly traces SFR averaged over 10 Myr timescales, whereas the UV-continuum over-predicts SFR on 100 Myr timescales at low stellar masses. These results point to our Hα sample undergoing ‘bursty’ star formation. Our F356W z ∼ 6 sample showed a larger scatter in $\rm {SFR_{10}/SFR_{100}}$ across all stellar masses, which has highlighted how narrow-band photometric selections of Hα emitters are key to quantifying the burstiness of star-formation activity.

Abstract:

The dipole anisotropy induced by our peculiar motion in the sky distribution of cosmologically distant sources is an important consistency test of the standard Friedmann-Lemaître-Robertson-Walker cosmology. In this work, we formalize how to compute the kinematic matter dipole in redshift bins. Apart from the usual terms arising from angular aberration and flux boosting, there is a contribution from the boosting of the redshifts that becomes important when considering a sample selected on observed redshift, leading to nonvanishing correction terms. We discuss examples and provide expressions to incorporate arbitrary redshift selection functions. We also discuss the effect of redshift measurement uncertainties in this context, in particular in upcoming surveys for which we provide estimates of the correction terms. Depending on the shape of a sample’s redshift distribution and on the applied redshift cuts, the correction terms can become substantial, even to the degree that the direction of the dipole is reversed. Lastly, we discuss how cuts on variables correlated with observed redshift, such as color, can induce additional correction terms. Published by the American Physical Society 2025

Abstract:

We present the first results of the H i intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering 4 square degrees in the COSMOS field using a frequency range of 962.5–1008.42 MHz, equivalent to H i emission in . The data consist of 15 pointings with a total of 94.2 h on-source. We verify the suitability of the MIGHTEE data for H i intensity mapping by testing for residual systematics across frequency, baselines, and pointings. We also vary the window used for H i signal measurements and find no significant improvement using stringent Fourier mode cuts. We compute the H i power spectrum at scales in autocorrelation as well as cross-correlation between observational scans using power spectrum domain averaging for pointings. We report consistent upper limits of 29.8 mK Mpc from the 2 cross-correlation measurements and 25.82 mK Mpc from autocorrelation at 2 Mpc.The low signal-to-noise ratio in this data potentially limits our ability to identify residual systematics, which will be addressed in the future by incorporating more data in the analysis.