Search

The formation of supermassive black holes (SMBHs) in the Universe and its role in the properties of the galaxies is one of the open questions in astrophysics and cosmology. Though, traditionally, electromagnetic waves have been instrumental in direct measurements of SMBHs, significantly influencing our comprehension of galaxy formation, gravitational waves (GW) bring an independent avenue to detect numerous binary SMBHs in the observable Universe in the nano-Hertz range using the pulsar timing array observation. This brings a new way to understand the connection between the formation of binary SMBHs and galaxy formation if we can connect theoretical models with multimessenger observations namely GW data and galaxy surveys. Along these lines, we present here the first paper on this series based on romulus25 cosmological simulation on the properties of the host galaxies of SMBHs and propose on how this can be used to connect with observations of nano-Hertz GW signal and galaxy surveys. We show that the most dominant contribution to the background will arise from sources with high chirp masses which are likely to reside in low-redshift early-type galaxies with high stellar mass, largely old stellar population, and low star formation rate, and that reside at centres of galaxy groups and manifest evidence of recent mergers. The masses of the sources show a correlation with the halo mass and stellar mass of the host galaxies. This theoretical study will help in understanding the host properties of the GW sources and can help in establishing a connection with observations. [ABSTRACT FROM AUTHOR]

This paper presents the third data release of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 52 ultra-compact massive galaxies (UCMGs) observed with the X-Shooter spectrograph. We measure integrated stellar velocity dispersion, [Mg/Fe] abundances, ages, and metallicities for all the INSPIRE objects. We thus infer star formation histories and confirm the existence of a degree of relicness (DoR), defined in terms of the fraction of stellar mass formed by z  = 2, the time at which a galaxy has assembled 75 per cent of its mass, and the final assembly time. Objects with a high DoR assembled their stellar mass at early epochs, while low-DoR objects show a non-negligible fraction of later formed populations and hence a spread in ages and metallicities. A higher DoR correlates with larger [Mg/Fe], supersolar metallicity, and larger velocity dispersion values. The 52 UMCGs span a large range of DoR from 0.83 to 0.06, with 38 of them having formed more than 75  per cent of their mass by z  = 2. Of these, nine are extreme relics (DoR>0.7), since they formed the totality (⁠|$\gt 99~{{\ \rm per\ cent}}$|⁠) of their stellar mass by redshift z  = 2. The remaining 14 UCMGs cannot be considered relics, as they are characterized by more extended star formation histories. With INSPIRE  we built the first sizeable sample of relics outside the local Universe, up to z ∼ 0.4, increasing the number of confirmed relics by a factor of >10, and opening up an important window to explain the mass assembly of massive galaxies in the high- z Universe. [ABSTRACT FROM AUTHOR]

With the launch of JWST and other scheduled missions aimed at probing the distant universe, we are entering a new promising era for high- z astronomy. One of our main goals is the detection of the first population of stars (Population III or Pop III stars), and models suggest that Pop III star formation is allowed well into the Epoch of Reionization (EoR), rendering this an attainable achievement. In this paper, we focus on our chance of detecting massive Pop IIIs at the moment of their death as Pair-Instability Supernovae (PISNe). We estimate the probability of discovering PISNe during the EoR in galaxies with different stellar masses (7.5 ≤ Log(M ⋆/M⊙) ≤ 10.5) from six dustyGadget simulations of 50  h −1 cMpc per side. We further assess the expected number of PISNe in surveys with JWST/NIRCam and Roman/WFI. On average, less than one PISN is expected in all examined JWST fields at z ≃ 8 with Δ z  = 1, and O(1) PISN may be found in a ∼1 deg2 Roman field in the best-case scenario, although different assumptions on the Pop III IMF and/or Pop III star formation efficiency can decrease this number substantially. Including the contribution from unresolved low-mass haloes holds the potential for increased discoveries. JWST/NIRCam and Roman/WFI allow the detection of massive-progenitor (∼250 M⊙) PISNe throughout all the optimal F200W-F356W, F277W-F444W, and F158-F213 colours. PISNe are also pre-dominantly located at the outskirts of their hosting haloes, facilitating the disentangling of underlying stellar emission thanks to the spatial-resolution capabilities of the instruments. [ABSTRACT FROM AUTHOR]

Low-metallicity very massive stars with an initial mass of ∼140– |$260\, \mathrm{M}_\odot$| are expected to end their lives as pair-instability supernovae (PISNe). The abundance pattern resulting from a PISN differs drastically from regular core-collapse supernova (CCSN) models and is expected to be seen in very metal-poor (VMP) stars of [Fe/H] ≲ −2. Despite the routine discovery of many VMP stars, the unique abundance pattern expected from PISNe has not been unambiguously detected. The recently discovered VMP star LAMOST J1010 + 2358, however, shows a peculiar abundance pattern that is remarkably well fit by a PISN, indicating the potential first discovery of a bonafide star born from gas polluted by a PISN. In this paper, we study the detailed nucleosynthesis in a large set of models of CCSN of Pop III and Pop II star of metallicity [Fe/H] = −3 with masses ranging from 12 to |$30\, \mathrm{M}_\odot$|⁠. We find that the observed abundance pattern in LAMOST J1010 + 2358 can be fit at least equally well by CCSN models of ∼12– |$14\, \mathrm{M}_\odot$| that undergo negligible fallback following the explosion. The best-fitting CCSN models provide a fit that is even marginally better than the best-fitting PISN model. We conclude the measured abundance pattern in LAMOST J1010 + 2358 could have originated from a CCSN and therefore cannot be unambiguously identified with a PISN given the set of elements measured in it to date. We identify key elements that need to be measured in future detections in stars like LAMOST J1010 + 2358 that can differentiate between CCSN and PISN origin. [ABSTRACT FROM AUTHOR]

The estimation of galaxy stellar masses depends on the assumed prior of the star-formation history (SFH) and spatial scale of the analysis (spatially resolved versus integrated scales). In this paper, we connect the prescription of the SFH in the spectral energy distribution (SED) fitting to spatially resolved scales (∼kpc) to shed light on the systematics involved when estimating stellar masses. Specifically, we fit the integrated photometry of ∼970 massive (log (M⋆/M⊙) = 9.8–11.5), intermediate redshift (z  = 0.5–2.0) galaxies with PROSPECTOR , assuming both exponentially declining tau model and flexible SFHs. We complement these fits with the results of spatially resolved SFH estimates obtained by pixel-by-pixel SED fitting, which assume tau models for individual pixels. These spatially resolved SFHs show a large diversity in shapes, which can largely be accounted for by the flexible SFHs with PROSPECTOR. The differences in the stellar masses from those two approaches are overall in good agreement (average difference of ∼0.07 dex). Contrarily, the simpler tau model SFHs typically miss the oldest episode of star formation, leading to an underestimation of the stellar mass by ∼0.3 dex. We further compare the derived global specific star-formation rate (sSFR), the mass-weighted stellar age (t50), and the star-formation time-scale (τSF) obtained from the different SFH approaches. We conclude that the spatially resolved scales within galaxies motivate a flexible SFH on global scales to account for the diversity of SFHs and counteract the effects of outshining of older stellar populations by younger ones. [ABSTRACT FROM AUTHOR]