Assessing the performance of forthcoming Infrared telescopes

Sterrenkunde is grotendeels gebaseerd op data-analyse en deze data zijn het product van onderzoek en ontwikkelingen in zowel natuurkunde als instrumenten. Dit proefschrift gaat in op verschillende onderdelen van deze procedure en focust op de twee aankomende infrarode instrumenten: de APEX Microgolf Infrarood Detector (A-MKID) voor de Atacama Pathfinder Experiment (APEX) en de James Webb Space Telescope (JWST). Omdat uit A-MKID een grotere verzameling detectoren bestaat dan conventionele infrarooddetectoren, zijn traditionele kalibratiemethodes niet geschikt. In mijn proefschrift presenteer ik een nieuwe kalibratiemethode voor A-MKID en een correctiemethode voor het “crosstalkeffect” in de A-MKID afbeeldingen (cross-talk refereert aan het onechte signaal dat wordt opgewekt in één detector als “echo” van het echte signaal in de andere chip). Daarnaast heb ik een aantal nuttige voorspellingen gemaakt voor het toekomstige ontwerp van toekomstige waarnemingen van de JWST. Deze telescoop zal verstaande sterrenstelsels kunnen waarnemen die vanaf 500 miljoen jaar na de oerknal aanwezig waren. In het bijzonder analyseer ik de mogelijkheid om verschillende sterrenstelseleigenschappen te ontdekken met JWST instrumenten. Tot slot bestudeer ik een verzameling van sterrenstelsels uit een periode die 11 miljard jaar beslaat om verschillende vormen van stervorming te analyseren. Deze vormen zijn een langzame vorm, waarin sterren gestaag gevormd worden, en een snelle vorm in welke sterren worden gecreëerd in een zogenaamde starburst. Ik vind dat starbursts gebruikelijker zijn dan eerder gedacht en dat ze belangrijk zijn in de kleinste sterrenstelsels. Al deze stappen onderstrepen het belang van infraroodinstrumenten en -data om sterrenstelselvorming en -evolutie in verschillende kosmische tijdsperken te bestuderen

Very compact millimeter sizes for composite star-forming/AGN submillimeter galaxies

We report the study of far-IR sizes of submillimeter galaxies (SMGs) in relation to their dust-obscured star formation rate (SFR) and active galactic nuclei (AGN) presence, determined using mid-IR photometry. We determined the millimeter-wave ($\lambda_{\rm obs}=1100 \mu$m) sizes of 69 ALMA-identified SMGs, selected with $\geq10$$\sigma$ confidence on ALMA images ($F_{\rm 1100 \mu m}=1.7$--7.4 mJy). We found that all the SMGs are located above an avoidance region in the millimeter size-flux plane, as expected by the Eddington limit for star formation. In order to understand what drives the different millimeter-wave sizes in SMGs, we investigated the relation between millimeter-wave size and AGN fraction for 25 of our SMGs at $z=1$--3. We found that the SMGs for which the mid-IR emission is dominated by star formation or AGN have extended millimeter-sizes, with respective median $R_{\rm c,e} = 1.6^{+0.34}_{-0.21}$ and 1.5$^{+0.93}_{-0.24}$ kpc. Instead, the SMGs for which the mid-IR emission corresponds to star-forming/AGN composites have more compact millimeter-wave sizes, with median $R_{\rm c,e}=1.0^{+0.20}_{-0.20}$ kpc. The relation between millimeter-wave size and AGN fraction suggests that this size may be related to the evolutionary stage of the SMG. The very compact sizes for composite star-forming/AGN systems could be explained by supermassive black holes growing rapidly during the SMG coalescing, star-formation phase.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in ApJ Lette

Expectations of the size evolution of massive galaxies at 3≤z≤63 \leq z \leq 6 from the TNG50 simulation: the CEERS/JWST view

We present a catalog of about 25,000 images of massive ($M_{\star} \ge 10^9 M_{\odot}$) galaxies at redshift $3 \leq z \leq 6$ from the TNG50 cosmological simulation, tailored for observations at multiple wavelengths carried out with JWST. The synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering. The noiseless images were processed with the mirage simulator to mimic the Near Infrared Camera (NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we analyze the predictions of the TNG50 simulation for the size evolution of galaxies at $3 \leq z \leq 6$ and the expectations for CEERS to probe that evolution. In particular, we investigate how sizes depend on wavelength, redshift, mass, and angular resolution of the images. We find that the effective radius accurately describes the three-dimensional half-mass radius of TNG50 galaxies. Sizes observed at 2~$\mu$m are consistent with those measured at 3.56~$\mu$m at all redshifts and masses. At all masses, the population of higher-$z$ galaxies is more compact than their lower-$z$ counterparts. However, the intrinsic sizes are smaller than the mock observed sizes for the most massive galaxies, especially at $z \lesssim 4$. This discrepancy between the mass and light distribution may point to a transition in the galaxy morphology at $z$=4-5, where massive compact systems start to develop more extended stellar structures.Comment: Accepted for publication in ApJ (20 pages, 12 figures). Data publicly released at https://www.tng-project.org/costantin22 and at https://www.lucacostantin.com/OMEG

Near-infrared emission line diagnostics for AGN from the local Universe to redshift 3

Optical rest-frame spectroscopic diagnostics are usually employed to distinguish between star formation and AGN-powered emission. However, this method is biased against dusty sources, hampering a complete census of the AGN population across cosmic epochs. To mitigate this effect, it is crucial to observe at longer wavelengths in the rest-frame near-infrared (near-IR), which is less affected by dust attenuation and can thus provide a better description of the intrinsic properties of galaxies. AGN diagnostics in this regime have not been fully exploited so far, due to the scarcity of near-IR observations of both AGNs and star-forming galaxies, especially at redshifts higher than 0.5. Using Cloudy photoionization models, we identify new AGN - star formation diagnostics based on the ratio of bright near-infrared emission lines, namely [SIII] 9530 Angstrom, [CI] 9850 Angstrom, [PII] 1.188 $\mu m$, [FeII] $1.257 \mu m$, and [FeII] $1.64 \mu m$ to Paschen lines (either Pa$\gamma$ or Pa$\beta$), providing simple, analytical classification criteria. We apply these diagnostics to a sample of 64 star-forming galaxies and AGNs at 0 < z < 1, and 65 sources at 1 < z < 3 recently observed with JWST-NIRSpec in CEERS. We find that the classification inferred from the near-infrared is broadly consistent with the optical one based on the BPT and the [SII]/H$\alpha$ ratio. However, in the near-infrared, we find $\sim 60 \%$ more AGNs than in the optical (13 instead of 8), with 5 sources classified as 'hidden' AGNs, showing a larger AGN contribution at longer wavelengths, possibly due to the presence of optically thick dust. The diagnostics we present provide a promising tool to find and characterize AGNs from z=0 to z=3 with low and medium-resolution near-IR spectrographs in future surveys.Comment: Paper accepted for publication in A&A on 05/09/2023. Three public Github repositories include: (1) a table with emission line measurements for the paper sample : https://github.com/Anthony96/Line_measurements_nearIR , Cloudy emission line predictions for star-forming galaxies and AGN models : https://github.com/Anthony96/star-forming_models , https://github.com/Anthony96/AGN_model

A z=1.85 galaxy group in CEERS: evolved, dustless, massive intra-halo light and a brightest group galaxy in the making

We present CEERS JWST/NIRCam imaging of a massive galaxy group at z=1.85, to explore the early JWST view on massive group formation in the distant Universe. The group contains >16 members (including 6 spectros. confirmations) down to log10(Mstar/Msun)=8.5, including the brightest group galaxy (BGG) in the process of actively assembling at this redshift. The BGG is comprised of multiple merging components extending ~3.6" (30kpc) across the sky. The BGG contributes 69% of the group's total galactic stellar mass, with one of the merging components containing 76% of the total mass of the BGG and a SFR>1810Msun/yr. Most importantly, we detect intra-halo light (IHL) in several HST and JWST/NIRCam bands, allowing us to construct a state-of-the-art rest-frame UV-NIR Spectral Energy Distribution of the IHL for the first time at this high redshift. This allows stellar population characterisation of both the IHL and member galaxies, as well as the morphology distribution of group galaxies vs. their star-formation activity when coupled with Herschel data. We create a stacked image of the IHL, giving us a sensitivity to extended emission of 28.5 mag/arcsec2 at rest-frame 1um. We find that the IHL is extremely dust poor (Av~0), containing an evolved stellar population of log10(t50/yr)=8.8, corresponding to a formation epoch for 50% of the stellar material 0.63Gyr before z=1.85. There is no evidence of ongoing star-formation in the IHL. The IHL in this group at z=1.85 contributes ~10% of the total stellar mass, comparable with what is observed in local clusters. This suggests that the evolution of the IHL fraction is more self-similar with redshift than predicted by some models, challenging our understanding of IHL formation during the assembly of high-redshift clusters. JWST is unveiling a new side of group formation at this redshift, which will evolve into Virgo-like structures in the local Universe.Comment: 14 pages + appendix, 11 figures, 4 tables. Accepted to A&A on 15th May 202

CEERS: Spatially Resolved UV and mid-IR Star Formation in Galaxies at 0.2 < z < 2.5: The Picture from the Hubble and James Webb Space Telescopes

We present the mid-IR (MIR) morphologies for 64 star-forming galaxies at 0.210^{9}~M_\odot} using JWST MIRI observations from the Cosmic Evolution Early Release Science survey (CEERS). The MIRI bands span the MIR (7.7--21~$\mu$m), enabling us to measure the effective radii ($R_{\rm{eff}}$) and S\'{e}rsic indexes of these SFGs at rest-frame 6.2 and 7.7 $\mu$m, which contains strong emission from Polycyclic aromatic hydrocarbon (PAH) features, a well-established tracer of star formation in galaxies. We define a ``PAH-band'' as the MIRI bandpass that contains these features at the redshift of the galaxy. We then compare the galaxy morphologies in the PAH-bands to those in rest-frame Near-UV (NUV) using HST ACS/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging from UVCANDELS and CANDELS, where the NUV-band and F160W trace the profile of (unobscured) massive stars and the stellar continuum, respectively. The $R_{\rm{eff}}$ of galaxies in the PAH-band are slightly smaller ($\sim$10\%) than those in F160W for galaxies with $\rm{M_*\gtrsim10^{9.5}~M_\odot}$ at $z\leq1.2$, but the PAH-band and F160W have a similar fractions of light within 1 kpc. In contrast, the $R_{\rm{eff}}$ of galaxies in the NUV-band are larger, with lower fractions of light within 1 kpc compared to F160W for galaxies at $z\leq1.2$. Using the MIRI data to estimate the $\rm{SFR_{\rm{IR}}}$ surface density, we find the correlation between the $\rm{SFR_{\rm{IR}}}$ surface density and stellar mass has a steeper slope than that of the $\rm{SFR_{\rm{UV}}}$ surface density and stellar mass, suggesting more massive galaxies having increasing amounts of obscured fraction of star formation in their inner regions. This paper demonstrates how the high-angular resolution data from JWST/MIRI can reveal new information about the morphology of obscured-star formation.Comment: 28 pages, 11 figures, Accepted by Ap

A Milky Way-like barred spiral galaxy at a redshift of 3

International audienceThe majority of massive disk galaxies in the local Universe show a stellar barred structure in their central regions, including our Milky Way. Bars are supposed to develop in dynamically cold stellar disks at low redshift, as the strong gas turbulence typical of disk galaxies at high redshift suppresses or delays bar formation. Moreover, simulations predict bars to be almost absent beyond $z = 1.5$ in the progenitors of Milky Way-like galaxies. Here we report observations of ceers-2112, a barred spiral galaxy at redshift $z_{\rm phot} \sim 3$, which was already mature when the Universe was only 2 Gyr old. The stellar mass ($M_{\star} = 3.9 \times 10^9 M_{\odot}$) and barred morphology mean that ceers-2112 can be considered a progenitor of the Milky Way, in terms of both structure and mass-assembly history in the first 2 Gyr of the Universe, and was the closest in mass in the first 4 Gyr. We infer that baryons in galaxies could have already dominated over dark matter at $z \sim 3$, that high-redshift bars could form in approximately 400 Myr and that dynamically cold stellar disks could have been in place by redshift $z = 4-5$ (more than 12 Gyrs ago)