arXiv subjects

C. Karoumpis

Publications and source records attributed to C. Karoumpis.

7 recordsLinked to original sources

arXiv2026

Spectral Data-cube Cleaning for CCAT Deep Spectroscopic Survey. I. Effect of correlated noise and filtering on the power spectrum

The Epoch of Reionization Spectrometer (EoR-Spec) on the Fred Young Submillimeter Telescope (FYST) will conduct the CCAT Deep Spectroscopic Survey (DSS) to perform line-intensity mapping of redshifted [C II] emission. Atmospheric $1/f$ noise and instrumental systematics affect power-spectrum recovery. We present realistic end-to-end simulations to quantify these effects and evaluate a Filter-and-Bin (F&B) pipeline. The simulated observations include instrument response, astrophysical emission, atmospheric noise, and observing strategy. The pipeline suppresses atmospheric $1/f$ noise by about four orders of magnitude at low temporal frequencies while leaving only minor residual correlated noise. For a single EoR-Spec module operating at 50% observing efficiency, the DSS is expected to detect the combined [C II] + CO power spectrum on shot-noise-dominated scales ($k > 0.1\,\mathrm{Mpc}^{-1}$). With two modules operating at full efficiency, detections are achievable over all targeted spatial scales. The transfer function exceeds 80% at $k \gtrsim 0.5\,\mathrm{Mpc}^{-1}$ but falls below 20% at $k \lesssim 0.1\,\mathrm{Mpc}^{-1}$, indicating significant suppression of large-scale modes. These results demonstrate that the F&B pipeline is effective for recovering the shot-noise regime, while improved map-making techniques will be required for accurate large-scale clustering measurements.

astro-ph.GA↗

arXiv2026

Testing masking effectiveness using multi-line image cubes based on COSMOS2020 for [CII] line intensity mapping at $z_{[CII]} > 3.5$

We created line intensity mapping intensity cubes for CO and [CII] emission lines using the COSMOS2020 galaxy catalogue, forming predictions based on empirical data, for observations from Prime-Cam mounted on the Fred Young Submm Telescope. We also included simulated noise including white and correlated components, and tested masking techniques to recover [CII] signal at $3.5<z<8.2$. We applied line luminosity models to the COSMOS2020 galaxy catalogue, spanning 1.44deg$^2$, to estimate the [CII] and CO J=1-0 emission, with other CO transitions derived using Spectral Line Energy Distribution templates. From these we made cubes for four 40 GHz bands in the EoR-Spec frequency range (205-420GHz), as well as a potential future upgrade to EoR-Spec including bands at 150 and 90GHz. Given the incompleteness of the empirical catalogue, these predictions are conservative lower limits, which we subsequently extrapolated from. We applied masks to recover the [CII] power spectra, using bright galaxies of COSMOS2020 as a foreground catalogue to target CO at low z (targeted masking), and matching bright voxels across frequency bands to eliminate those associated with CO emission (blind masking). Our CO intensity cube predictions are consistent with ALMA, VLA and NOEMA observations, indicating that this method gives realistic CO estimates for E-COSMOS. In ideal conditions, masking can recover [CII] above 300GHz, with targeted masking requiring a complete foreground catalogue of bright CO sources to prevent them from contributing to contaminant emission, and blind masking needing additional lower frequency ranges to be effective. However, noise will hinder [CII] recovery above 300 GHz until near the end of the currently planned 2000 hour observing period, as $S/N<5$ without extra observing time. Whilst CO can be recovered below 300GHz, [CII] will be unavailable without cross correlation techniques.

astro-ph.GA↗

arXiv2024

[CII] line intensity mapping the epoch of reionization with the Prime-Cam on FYST II. CO foreground masking based on an external catalog

Context. The Fred Young Submillimeter Telescope (FYST) line intensity mapping (LIM) survey will measure the power spectrum (PS) of the singly ionized carbon 158 $\rm μ$m fine-structure line, [CII], to trace the appearance of the first galaxies that emerged during and right after the epoch of reionization (EoR, $6<z<9$). Aims. We aim to quantify the contamination of the (post-)EoR [CII] LIM signal by foreground carbon monoxide (CO) line emission ($3 < J_{ \rm up} < 12$) and assess the efficiency to retrieve this [CII] LIM signal by the targeted masking of bright CO emitters. Methods. Using the IllustrisTNG300 simulation, we produced mock CO intensity tomographies based on empirical star formation rate-to-CO luminosity relations. Combining these predictions with the [CII] PS predictions of the first paper of this series, we evaluated a masking technique where the interlopers are identified and masked using an external catalog whose properties are equivalent to those of a deep Euclid survey. Results. Prior to masking, our [CII] PS forecast is an order of magnitude lower than the predicted CO contamination in the 225 GHz ([CII] emitted at $z=6.8-8.3$) band of the FYST LIM survey, at the same level in its 280 GHz ([CII] emitted at $z=5.3-6.3$) and 350 GHz ([CII] emitted at $z=4.1-4.8$) bands, and an order of magnitude higher in its 410 GHz ([CII] emitted at $z=3.4-3.9$) band. For our fiducial model, the optimal masking depth is reached when less than 10\% of the survey volume is masked at 350 and 410 GHz but around 40\% at 280 GHz and 60 \% at 225 GHz. At these masking depths we anticipate a detection of the [CII] PS at 350 and 410 GHz, a tentative detection at 280 GHz, whereas at 225 GHz the CO signal still dominates our model. In the last case, alternative decontamination techniques will be needed.

astro-ph.GA↗

arXiv2024

[CII] luminosity models and large-scale image cubes based on COSMOS 2020 and ALPINE-ALMA [CII] data back to the epoch of reionisation

We have implemented a novel method to create simulated [CII] emission line intensity mapping (LIM) data cubes using COSMOS 2020 galaxy catalogue data. It allows us to provide solid lower limits for previous simulation-based model predictions and the expected signal strength of upcoming surveys. We applied [CII]158$μ$m luminosity models to COSMOS 2020 to create LIM cubes covering a 1.2$\times$1.2 deg$^2$ sky area. These models were derived using galaxy bulk property data from the ALPINE-ALMA survey over the redshift range $4.4 1 when using FYST parameters. However, our high-redshift results remain inconclusive because of the poor completeness of COSMOS 2020 at $z$>6.3. These predictions will be improved on the basis of future JWST data.

astro-ph.GA↗

arXiv2022

CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope

We present a detailed overview of the science goals and predictions for the Prime-Cam direct detection camera/spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6-m aperture submillimeter telescope being built (first light in mid-2024) by an international consortium of institutions led by Cornell University and sited at more than 5600 meters on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way galaxy. Prime-Cam on the FYST will have a mapping speed that is over ten times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies above 300 GHz. We describe details of the science program enabled by this system and our preliminary survey strategies.

astro-ph.CO↗

arXiv2021

[CII] line intensity mapping the epoch of reionization with the Prime-Cam on FYST

We predict the three-dimensional intensity power spectrum (PS) of the [CII] 158$\,μ$m line throughout the epoch of (and post) reionization at redshifts from $\approx$ 3.5 to 8. We study the detectability of the PS in a line intensity mapping (LIM) survey with the Fred Young Submillimeter Telescope (FYST). We created mock [CII] tomographic scans in redshift bins at $z\approx$ 3.7, 4.3, 5.8, and 7.4 using the Illustris TNG300-1 $Λ$CDM simulation and adopting a relation between the star formation activity and the [CII] luminosity ($L_{[CII]}$) of galaxies. A star formation rate (SFR) was assigned to a dark matter halo in the Illustris simulation in two ways: (i) we adopted the SFR computed in the Illustris simulation and, (ii) we matched the abundance of the halos with the SFR traced by the observed dust-corrected ultraviolet luminosity function of high-redshift galaxies. The $L_{[CII]}$ is related to the SFR from a semi-analytic model of galaxy formation, from a hydrodynamical simulation of a high-redshift galaxy, or from a high-redshift [CII] galaxy survey. The [CII] intensity PS was computed from mock tomographic scans to assess its detectability with the anticipated observational capability of the FYST. The amplitude of the predicted [CII] intensity power spectrum varies by more than a factor of 10, depending on the choice of the halo-to-galaxy SFR and the SFR-to-$L_{[CII]}$ relations. In the planned $4^{\circ} \times 4^{\circ}$ FYST LIM survey, we expect a detection of the [CII] PS up to $z \approx$ 5.8, and potentially even up to $z \approx $ 7.4. The design of the envisioned FYST LIM survey enables a PS measurement not only in small (<10 Mpc) shot noise-dominated scales, but also in large (>50 Mpc) clustering-dominated scales making it the first LIM experiment that will place constraints on the SFR-to-$L_{[CII]}$ and the halo-to-galaxy SFR relations simultaneously.

astro-ph.GA↗

arXiv2019

Radio continuum size evolution of star-forming galaxies over 0.35 < z < 2.25

We present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range $0.35<z<2.25$. We use the VLA COSMOS 3GHz map (noise $\rm rms=2.3\,μJy \,beam^{-1}$, $θ_{\rm beam}=0.75\,\rm arcsec$) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main-sequence (MS) of SFGs. We find no clear dependence between the radio size and stellar mass, $M_{\star}$, of SFGs with $10.5\lesssim\log(M_\star/\rm M_\odot)\lesssim11.5$. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of $R_{\rm eff}=1.5\pm0.2$ ($1.0\pm0.2$) kpc remains nearly constant with cosmic time; a parametrization of the form $R_{\rm eff}\propto(1+z)^α$ yields a shallow slope of only $α=-0.26\pm0.08\,(0.12\pm0.14)$ for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than the extent of the radio continuum emission by a factor $\sim$2 (1.3) at $z=0.5\,(2)$, indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density $(Σ_{\rm SFR})$ scales with the distance to the MS, except for a fraction of MS galaxies ($\lesssim10\%$) that harbor starburst-like $Σ_{\rm SFR}$. These "hidden" starbursts might have experienced a compaction phase due to disk instability and/or merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to jointly use $Σ_{\rm SFR}$ and distance to the MS to better identify the galaxy population undergoing a starbursting phase.

astro-ph.GA↗