Abstract
Here we investigate the evolution of a Milky Way (MW)-like galaxy with the aim of predicting the properties of its progenitors all the way from z ∼ 20 to z = 0. We apply gamesh to a ...high-resolution N-body simulation following the formation of a MW-type halo and we investigate its properties at z ∼ 0 and its progenitors in 0 < z < 4. Our model predicts the observed galaxy main sequence, the mass–metallicity and the Fundamental Plane of metallicity relations in 0 < z < 4. It also reproduces the stellar mass evolution of candidate MW progenitors in 0 ≲ z ≲ 2.5, although the star formation rate and gas fraction of the simulated galaxies follow a shallower redshift dependence. We find that while the MW star formation and chemical enrichment are dominated by the contribution of galaxies hosted in Lyman α cooling haloes, at z > 6 the contribution of star-forming minihaloes is comparable to the star formation rate along the MW merger tree. These systems might then provide an important contribution in the early phases of reionization. A large number of minihaloes with old stellar populations, possibly Population III stars, are dragged into the MW or survive in the Local Group. At low redshift dynamical effects, such as halo mergers, tidal stripping and halo disruption redistribute the baryonic properties among halo families. These results are critically discussed in light of future improvements including a more sophisticated treatment of radiative feedback and inhomogeneous metal enrichment.
The origin of carbon-enhanced metal-poor (CEMP) stars and their possible connection with the chemical elements produced by the first stellar generation is still highly debated. In contrast to the ...Galactic halo, not many CEMP stars have been found in the dwarf spheroidal galaxies around the Milky Way. Here we present detailed abundances from ESO VLT/UVES high-resolution spectroscopy for ET0097, the first CEMP star found in the Sculptor dwarf spheroidal, which is one of the best studied dwarf galaxies in the Local Group. This star has Fe/H = −2.03 ± 0.10, C/Fe = 0.51 ± 0.10 and N/Fe = 1.18 ± 0.20, which is the first nitrogen measurement in this galaxy. The traditional definition of CEMP stars is C/Fe ≥ 0.70, but taking into account that this luminous red giant branch star has undergone mixing, it was intrinsically less nitrogen enhanced and more carbon-rich when it was formed, and so it falls under the definition of CEMP stars, as proposed by Aoki et al. (2007, ApJ, 655, 492) to account for this effect. By making corrections for this mixing, we conclude that the star had C/Fe ≈ 0.8 during its earlier evolutionary stages. Apart from the enhanced C and N abundances, ET0097 shows no peculiarities in other elements lighter than Zn, and no enhancement of the heavier neutron-capture elements (Ba, La, Ce, Nd, Sm, Eu, Dy), making this a CEMP-no star. However, the star does show signs of the weak r-process, with an overabundance of the lighter neutron-capture elements (Sr, Y, Zr). To explain the abundance pattern observed in ET0097, we explore the possibility that this star was enriched by primordial stars. In addition to the detailed abundances for ET0097, we present estimates and upper limits for C abundances in 85 other stars in Sculptor derived from CN molecular lines, including 11 stars with Fe/H ≤ −2. Combining these limits with observations from the literature, the fraction of CEMP-no stars in Sculptor seems to be significantly lower than in the Galactic halo.
ABSTRACT
We use high-resolution (≈10 pc), zoom-in simulations of a typical (stellar mass $M_\star \simeq 10^{10}\, {\rm M}_{\odot }$) Lyman Break Galaxy (LBG) at z ≃ 6 to investigate the stellar ...populations of its six dwarf galaxy satellites, whose stellar gas masses are in the range log (M⋆/M⊙) ≃ 6−9 log (Mgas/M⊙) ≃ 4.3−7.75. The properties and evolution of satellites show no dependence on the distance from the central massive LBG (<11.5 kpc). Instead, their star formation and chemical enrichment histories are tightly connected to their stellar (and sub-halo) mass. High-mass dwarf galaxies ($M_\star \gtrsim 5\times 10^8 \, {\rm M}_{\odot }$) experience a long history of star formation, characterized by many merger events. Lower mass systems go through a series of short star formation episodes, with no signs of mergers; their star formation activity starts relatively late (z ≈ 7), and it is rapidly quenched by internal stellar feedback. In spite of the different evolutionary patterns, all satellites show a spherical morphology, with ancient and more metal-poor stars located towards the inner regions. All six dwarf satellites experienced high star formation rate ($\rm \gt 5\, {\rm M}_{\odot }\, {\rm yr}^{-1}$) bursts, which can be detected by James Webb Space Telescope while targeting high-z LBGs.
ABSTRACT
We present the results from the search for Lyman alpha emitters (LAEs) in the proximity of 11 C iv absorption systems at z > 4.7 in the spectrum of the QSO J1030+0524, using data from ...Multi-Unit Spectroscopic Explorer. We have found multiple LAE candidates close to four C iv systems at $z_{{\rm{C {\small IV}}}=4.94$–5.74 with $\log _{10}(N_{{\rm{C {\small IV}}}$cm−2) > 13.5. At z = 5–6, C iv systems with W$_0({\rm{C {\small IV}}})\gt 0.2$ Å seem more likely to have galaxies with Ly α emission within ρ < 200 proper kpc (4/5 cases) than the C iv systems with W$_0({\rm{C {\small IV}}})\lt 0.2$ Å (0/6 cases). The impact parameter of LAE–C iv systems with equivalent widths W0(C iv) > 0.5 Å is in the range $11\, \lesssim \, \rho \, \lesssim \, 200$ proper kpc (pkpc). Furthermore, all candidates are in the luminosity range 0.18–1.15 L$^{\star }_{\rm{{Ly\alpha}}}(z=5.7)$, indicating that the environment of C iv systems within 200 pkpc is populated by the faint end of the Ly α luminosity function. We report a 0.28 L$^{\star }_{\rm{{Ly\alpha}}}$ galaxy at a separation of ρ = 11 pkpc from a strong C iv absorption ($\log _{10}(N_{{\rm{C {\small IV}}}$cm−2) = 14.52) at $z_{{\rm{C {\small IV}}}=5.72419$. The prevalence of sub-L$^{\star }_{\rm{{Ly\alpha}}}$ galaxies in the proximity of z > 4.9 C iv systems suggest that the absorbing material is rather young, likely ejected in the recent past of the identified galaxies. The connection between faint LAEs and high-ionization absorption systems reported in this work is potentially a consequence of the role of low-mass galaxies in the early evolution of the circum-galactic and intergalactic media.
ABSTRACT
The very massive first stars (m > 100 $\rm M_{\odot }$) were fundamental to the early phases of reionization, metal enrichment, and supermassive black hole formation. Among them, those with ...$140\le \rm m/\rm M_{\odot }\le 260$ are predicted to evolve as Pair Instability Supernovae (PISN) leaving a unique chemical signature in their chemical yields. Still, despite long searches, the stellar descendants of PISN remain elusive. Here we propose a new methodology, the PISN-explorer, to identify candidates for stars with a dominant PISN enrichment. The PISN-explorer is based on a combination of physically driven models, and the FERRE code; and applied to data from large spectroscopic surveys (APOGEE, GALAH, GES, MINCE, and the JINA data base). We looked into more than 1.4 million objects and built a catalogue with 166 candidates of PISN descendants. One of which, 2M13593064+3241036, was observed with UVES at VLT and full chemical signature was derived, including the killing elements, Cu and Zn. We find that our proposed methodology is efficient in selecting PISN candidates from both the Milky Way and dwarf satellite galaxies such as Sextans or Draco. Further high-resolution observations are highly required to confirm our best selected candidates, therefore allowing us to probe the existence and properties of the very massive First Stars.
The energy distribution of the first supernovae Koutsouridou, I; Salvadori, S; Skúladóttir, Á ...
Monthly notices of the Royal Astronomical Society,
08/2023, Letnik:
525, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
The nature of the first Pop III stars is still a mystery and the energy distribution of the first supernovae is completely unexplored. For the first time we account simultaneously for the ...unknown initial mass function (IMF), stellar mixing, and energy distribution function (EDF) of Pop III stars in the context of a cosmological model for the formation of a MW-analogue. Our data-calibrated semi-analytic model is based on a N-body simulation and follows the formation and evolution of both Pop III and Pop II/I stars in their proper time-scales. We discover degeneracies between the adopted Pop III unknowns, in the predicted metallicity and carbonicity distribution functions and the fraction of C-enhanced stars. None the less, we are able to provide the first available constraints on the EDF, $dN/dE_\star \propto E_{\star }^{-\alpha _e}$ with 1 ≤ αe ≤ 2.5. In addition, the characteristic mass of the Pop III IMF should be mch < 100 M⊙, assuming a mass range consistent with hydrodynamical simulations (0.1–1000 M⊙). Independent of the assumed Pop III properties, we find that all $\rm C/Fe\gt +0.7$ stars (with $\rm Fe/H\lt -2.8$) have been enriched by Pop III supernovae at a $\gt 20~{{\ \rm per\ cent}}$ level, and all $\rm C/Fe\gt +2$ stars at a $\gt 95~{{\ \rm per\ cent}}$ level. All very metal-poor stars with $\rm C/Fe\lt 0$ are predicted to be predominantly enriched by Pop III hypernovae and/or pair instability supernovae. To better constrain the primordial EDF, it is absolutely crucial to have a complete and accurate determination of the metallicity distribution function, and the properties of C-enhanced metal-poor stars (frequency and C/Fe) in the Galactic halo.
Abstract
Eridanus II (Eri II) is an ultrafaint dwarf (UFD) galaxy (
M
V
= −7.1) located at a distance close to the Milky Way virial radius. Early shallow color–magnitude diagrams (CMDs) indicated ...that it possibly hosted an intermediate-age or even young stellar population, which is unusual for a galaxy of this mass. In this paper, we present new Hubble Space Telescope/Advanced Camera for Surveys CMDs reaching the oldest main-sequence turnoff with excellent photometric precision and derive a precise star formation history (SFH) for this galaxy through CMD fitting. This SFH shows that the bulk of the stellar mass in Eri II formed in an extremely short star formation burst at the earliest possible time. The derived star formation rate profile has a width at half maximum of 500 Myr and reaches a value compatible with null star formation 13 Gyr ago. However, tests with mock stellar populations and with the CMD of the globular cluster M92 indicate that the star formation period could be shorter than 100 Myr. From the quantitative determination of the amount of mass turned into stars in this early star formation burst ( ∼2 × 10
5
M
⊙
) we infer the number of supernova (SN) events and the corresponding energy injected into the interstellar medium. For reasonable estimates of the Eri II virial mass and values of the coupling efficiency of the SN energy, we conclude that Eri II could be quenched by SN feedback alone, thus casting doubts on the need to invoke cosmic reionization as the preferred explanation for the early quenching of old UFD galaxies.
Opioid receptors are currently classified as µ (mu: mOP), δ (delta: dOP), κ (kappa: kOP) with a fourth related non-classical opioid receptor for nociceptin/orphainin FQ, NOP. Morphine is the current ...gold standard analgesic acting at MOP receptors but produces a range of variably troublesome side-effects, in particular tolerance. There is now good laboratory evidence to suggest that blocking DOP while activating MOP produces analgesia (or antinociception) without the development of tolerance. Simultaneous targeting of MOP and DOP can be accomplished by: (i) co-administering two selective drugs, (ii) administering one non-selective drug, or (iii) designing a single drug that specifically targets both receptors; a bivalent ligand. Bivalent ligands generally contain two active centres or pharmacophores that are variably separated by a chemical spacer and there are several interesting examples in the literature. For example linking the MOP agonist oxymorphone to the DOP antagonist naltrindole produces a MOP/DOP bivalent ligand that should produce analgesia with reduced tolerance. The type of response/selectivity produced depends on the pharmacophore combination (e.g. oxymorphone and naltrindole as above) and the space between them. Production and evaluation of bivalent ligands is an emerging field in drug design and for anaesthesia, analgesics that are designed not to be highly selective morphine-like (MOP) ligands represents a new avenue for the production of useful drugs for chronic (and in particular cancer) pain.
Aims. A probable carbon enhanced metal-poor (CEMP) star, Pisces II 10694, was discovered recently in the ultra-faint (UFD) galaxy Pisces II. This galaxy is supposed to be very old, suspected to ...include dark matter, and likely formed the bulk of its stars before the reionisation of the Universe. Methods. New abundances have been obtained from observations of Pisces II 10694 at the Kueyen ESO VLT telescope, using the high-efficiency spectrograph: X-shooter. Results. We found that Pisces II 10694 is a CEMP-no star with Fe/H = −2.60 dex. Careful measurements of the CH and C2 bands confirm the enhancement of the C abundance (C/Fe = +1.23). This cool giant has very probably undergone extra mixing and thus its original C abundance could be even higher. Nitrogen, O, Na, and Mg are also strongly enhanced, but from Ca to Ni the ratios X/Fe are similar to those observed in classical very metal-poor stars. With its low Ba abundance (Ba/Fe = −1.10 dex) Pisces II 10694 is a CEMP-no star. No variation in the radial velocity could be detected between 2015 and 2017. The pattern of the elements has a shape similar to the pattern found in galactic CEMP-no stars like CS 22949-037 (Fe/H = −4.0) or SDSS J1349+1407 (Fe/H = −3.6). Conclusions. The existence of a CEMP-no star in the UFD galaxy Pisc II suggests that this small galaxy likely hosted zero-metallicity stars. This is consistent with theoretical predictions of cosmological models supporting the idea that UFD galaxies are the living fossils of the first star-forming systems.
CR7 is the brightest z = 6.6 Ly ... emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation ...using cosmological hydrodynamical simulations. Several simulated galaxies show the same 'Pop III wave' pattern observed in CR7. However, to reproduce the extreme CR7 Ly.../He ii1640 line luminosities ($L_...\rm \alpha /He\,\small ...II...$) a top-heavy initial mass function and a massive ( ... 10... M...) Pop III burst with age ... 2 Myr are required. Assuming that the observed properties of Ly ... and He ii emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with L... > 10... erg s... should also host Pop III stars producing an observable $L_...\rm He\,\small ...II...\gtrsim 10 greater than or equal to ..42.7...\,...\rm erg...\,...\rm s... greater than or equal to ..-1...$. As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts L..., $L_...\rm He\,\small ...II...$, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios. (ProQuest: ... denotes formulae/symbols omitted.)
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