Lack of influence of the environment in the earliest stages of massive galaxy formation

We investigate how the environment affects the assembly history of massive galaxies. For that purpose, we make use of SHARDS and HST spectro-photometric data, whose depth, spectral resolution, and wavelength coverage allow to perform a detailed analysis of the stellar emission as well as obtaining unprecedentedly accurate photometric redshifts. This expedites a sufficiently accurate estimate of the local environment and a robust derivation of the star formation histories of a complete sample of 332 massive galaxies ($\mathrm{>10^{10}M_{\odot}}$) at redshift $1\leq z \leq 1.5$ in the GOODS-N field. We find that massive galaxies in this redshift range avoid the lowest density environments. Moreover, we observed that the oldest galaxies in our sample with with mass-weighted formation redshift $\mathrm{\overline{z}_{M-w} \geq 2.5}$, avoid the highest density regions, preferring intermediate environments. Younger galaxies, including those with active star formation, tend to live in denser environments ($\Sigma = \mathrm{5.0_{1.1}^{24.8}\times 10^{10}M_{\odot}Mpc^{-2}}$). This behavior could be expected if those massive galaxies starting their formation first would merge with neighbors and sweep their environment earlier. On the other hand, galaxies formed more recently ($\overline{z}_{M-w} < 2.5$) are accreted into large scale structures at later times and we are observing them before sweeping their environment or, alternatively, they are less likely to affect their environment. However, given that both number and mass surface densities of neighbor galaxies is relatively low for the oldest galaxies, our results reveal a very weak correlation between environment and the first formation stages of the earliest massive galaxies.Comment: Accepted for publication in MNRA

Towards a new classification of galaxies: principal component analysis of CALIFA circular velocity curves

We present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto Legacy Integral Field Area) galaxies based on the shapes and amplitudes of their circular velocity curves (CVCs). We infer the CVCs from the de-projected surface brightness of the galaxies, after scaling by a constant mass-to-light ratio based on stellar dynamics - solving axisymmetric Jeans equations via fitting the second velocity moment $V_{\mathrm{rms}}=\sqrt{V^2+\sigma^2}$ of the stellar kinematics. We use principal component analysis (PCA) applied to the CVC shapes to find characteristic features and use a $k$-means classifier to separate circular curves into classes. This objective classification method identifies four different classes, which we name slow-rising (SR), flat (FL), round-peaked (RP) and sharp-peaked (SP) circular curves. SR are typical for low-mass, late-type (Sb-Sdm), young, faint, metal-poor and disc-dominated galaxies. SP are typical for high-mass, early-type (E1-E7), old, bright, metal-rich and bulge-dominated galaxies. FL and RP appear presented by galaxies with intermediate mass, age, luminosity, metallicity, bulge-to-disk ratio and morphologies (E4-S0a, Sa-Sbc). The discrepancy mass factor, $f_d=1-M_{*}/M_{dyn}$, have the largest value for SR and SP classes ($\sim$ 74 per cent and $\sim$ 71 per cent, respectively) in contrast to the FL and RP classes (with $\sim$ 59 per cent and $\sim$ 61 per cent, respectively). Circular curve classification presents an alternative to typical morphological classification and appears more tightly linked to galaxy evolution.Comment: Accepted for publication in MNRAS (Minor changes), 123 pages, 19 figures, 87 Tables (containing the basic properties of the 238 E1-Sdm galaxies; the five main Principal Component Eigenvectors; the five main Principal Components - PC_i; the Multi-Gaussian Expansion models - MGEs; the circular velocity curve models and their uncertainties

Probing the Star Formation Main Sequence down to 10810^{8} M⊙_\odot at 1.0<z<3.01.0<z<3.0

We investigate the star formation main sequence (MS) (SFR-M$_{\star}$) down to 10$^{8-9}\mathrm{M}_\odot$ using a sample of 34,061 newly-discovered ultra-faint ($27\lesssim i \lesssim 30$ mag) galaxies at $1<z<3$ detected in the GOODS-N field. Virtually these galaxies are not contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broad-band observations taken by the HST/GOODS-CANDELS surveys as well as the 25 ultra-deep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes $\sim28.2$ mag, $\sim27.9$ mag), blue (UV-slope $\sim-1.9$), star-forming (rest-frame colors $\sim0.10$ mag, $\sim0.17$ mag) galaxies. These observational characteristics are identified with young (mass-weighted age $\sim0.014$ Gyr) stellar populations subject to low attenuations ($\sim0.30$ mag). Our sample allows us to probe the MS down to $10^{8.0}\,\mathrm{M}_\odot$ at $z=1$ and $10^{8.5}\,\mathrm{M}_\odot$ at $z=3$, around 0.6 dex deeper than previous analysis. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at $1<z<2$ and 1.12 at $2<z<3$. Nearly $\sim$60% of our sample presents stellar masses in the range $10^{6-8}$ M$_\odot$ between $1<z<3$. If the slope of the MS remained constant in this regime, the sources populating the low-mass tail of our sample would qualify as starburst galaxies.Comment: 34 pages, 16 figures, 9 tables. Accepted for publication to Ap

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

Probing the earliest phases in the formation of massive galaxies with simulated HST+JWST imaging data from Illustris

We use the Illustris-1 simulation to explore the capabilities of the $\textit{Hubble}$ and $\textit{James Webb Space Telescope}$ data to analyze the stellar populations in high-redshift galaxies, taking advantage of the combined depth, spatial resolution, and wavelength coverage. For that purpose, we use simulated broad-band ACS, WFC3 and NIRCam data and 2-dimensional stellar population synthesis (2D-SPS) to derive the integrated star formation history (SFH) of massive (M$_{\ast}>10^{10}\,$M$_{\odot}$) simulated galaxies at $110^{11}\,$M$_{\odot}$ galaxy. In particular, we explore the potential of HST and JWST datasets reaching a depth similar to those of the CANDELS and ongoing CEERS observations, respectively, and concentrate on determining the capabilities of this dataset for characterizing the first episodes in the SFH of local M$_{\ast}>10^{11}\,$M$_{\odot}$ galaxies by studying their progenitors at $z>1$. The 2D-SPS method presented in this paper has been calibrated to robustly recover the cosmic times when the first star formation episodes occurred in massive galaxies, i.e., the first stages in their integrated SFHs. In particular, we discuss the times when the first 1% to 50% of their total stellar mass formed in the simulation. We demonstrate that we can recover these ages with typical median systematic offset of less than 5% and scatter around 20%-30%. According to our measurements on Illustris data, we are able to recover that local M$_{\ast}>10^{11}\,$M$_{\odot}$ galaxies would have started their formation by $z=16$, forming the first 5% of their stellar mass present at $z \sim 1$ by $z=4.5$, 10% by $z=3.7$, and 25% by $z=2.7$.Comment: 28 pages, 13 figures, 4 tables. ApJ in press. Summary of changes from original submission: the major change is that we now include in Sec. 6 the comparison of the results obtained for our sample of massive 1 < z < 4 progenitors with those obtained by considering all massive galaxies at 1 < z < 4 in the simulated images. Several figures and sections have been update

A duality in the origin of bulges and spheroidal galaxies

Studying the resolved stellar populations of the different structural components which build massive galaxies directly unveils their assembly history. We aim at characterizing the stellar population properties of a representative sample of bulges and pure spheroids in massive galaxies (M* > 10^(10) Mסּ ) in the GOODS-N field. We take advantage of the spectral and spatial information provided by SHARDS and HST data to perform the multi-image spectro-photometrical decoupling of the galaxy light. We derive the spectral energy distribution separately for bulges and disks in the redshift range 0.14 < z ≤1 with spectral resolution R ∼50. Analyzing these SEDs, we find evidences of a bimodal distribution of bulge formation redshifts. We find that 33% of them present old mass-weighted ages, implying a median formation redshift z_(form) = 6.2^(+1.5)_(−1.7). They are relics of the early Universe embedded in disk galaxies. A second wave, dominant in number, accounts for bulges formed at median redshift z_(form) = 1.3^(+0.6)_(−0.6). The oldest (1st-wave) bulges are more compact than the youngest. Virtually all pure spheroids (i.e., those without any disk) are coetaneous with the 2nd-wave bulges, presenting a median redshift of formation z_(form) = 1.1^(+0.3)_(−0.3). The two waves of bulge formation are not only distinguishable in terms of stellar ages, but also in star formation mode. All 1st-wave bulges formed fast at z ∼ 6, with typical timescales around 200 Myr. A significant fraction of the 2nd-wave bulges assembled more slowly, with star formation timescales as long as 1 Gyr. The results of this work suggest that the centers of massive disk-like galaxies actually harbor the oldest spheroids formed in the Universe

MIDIS: JWST/MIRI reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble-UDF at Cosmic Noon

We present deep James Webb Space Telescope (JWST)/MIRI F560W observations of a flux-limited, ALMA-selected sample of 28 galaxies at z=0.5-3.6 in the Hubble Ultra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS) reveal the stellar structure of the HUDF galaxies at rest-wavelengths of >1 micron for the first time. We revise the stellar mass estimates using new JWST photometry and find good agreement with pre-JWST analysis; the few discrepancies can be explained by blending issues in the earlier lower-resolution Spitzer data. At z~2.5, the resolved rest-frame near-infrared (1.6 micron) structure of the galaxies is significantly more smooth and centrally concentrated than seen by HST at rest-frame 450 nm (F160W), with effective radii of Re(F560W)=1-5 kpc and S\'ersic indices mostly close to an exponential (disk-like) profile (n~1), up to n~5 (excluding AGN). We find an average size ratio of Re(F560W)/Re(F160W)~0.7 that decreases with stellar mass. The stellar structure of the ALMA-selected galaxies is indistinguishable from a HUDF reference sample of galaxies with comparable MIRI flux density. We supplement our analysis with custom-made, position-dependent, empirical PSF models for the F560W observations. The results imply that an older and smoother stellar structure is in place in massive gas-rich, star-forming galaxies at Cosmic Noon, despite a more clumpy rest-frame optical appearance, placing additional constraints on galaxy formation simulations. As a next step, matched-resolution, resolved ALMA observations will be crucial to further link the mass- and light-weighted galaxy structures to the dusty interstellar medium.Comment: 19 pages, 10 figures, 1 table, submitted to Ap

CEERS: 7.7 μ{\mu}m PAH Star Formation Rate Calibration with JWST MIRI

We test the relationship between UV-derived star formation rates (SFRs) and the 7.7 ${\mu}$m polycyclic aromatic hydrocarbon (PAH) luminosities from the integrated emission of galaxies at z ~ 0 - 2. We utilize multi-band photometry covering 0.2 - 160 ${\mu}$m from HST, CFHT, JWST, Spitzer, and Herschel for galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We perform spectral energy distribution (SED) modeling of these data to measure dust-corrected far-UV (FUV) luminosities, $L_{FUV}$, and UV-derived SFRs. We then fit SED models to the JWST/MIRI 7.7 - 21 ${\mu}$m CEERS data to derive rest-frame 7.7 ${\mu}$m luminosities, $L_{770}$, using the average flux density in the rest-frame MIRI F770W bandpass. We observe a correlation between $L_{770}$ and $L_{FUV}$, where log $L_{770}$ is proportional to (1.27+/-0.04) log $L_{FUV}$. $L_{770}$ diverges from this relation for galaxies at lower metallicities, lower dust obscuration, and for galaxies dominated by evolved stellar populations. We derive a "single-wavelength" SFR calibration for $L_{770}$ which has a scatter from model estimated SFRs (${{\sigma}_{{\Delta}SFR}}$) of 0.24 dex. We derive a "multi-wavelength" calibration for the linear combination of the observed FUV luminosity (uncorrected for dust) and the rest-frame 7.7 ${\mu}$m luminosity, which has a scatter of ${{\sigma}_{{\Delta}SFR}}$ = 0.21 dex. The relatively small decrease in ${\sigma}$ suggests this is near the systematic accuracy of the total SFRs using either calibration. These results demonstrate that the rest-frame 7.7 ${\mu}$m emission constrained by JWST/MIRI is a tracer of the SFR for distant galaxies to this accuracy, provided the galaxies are dominated by star-formation with moderate-to-high levels of attenuation and metallicity.Comment: 20 pages, 11 figures, 2 tables, submitted to Ap