اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe metallicity properties of simulated long-GRB galaxy hosts and the Fundamental Metallicity Relation
191
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We study the implication of the collapsar model for Long Gamma-Ray Bursts (LGRBs) on the metallicity properties of the host galaxies, by combining high-resolution N-body simulations with semi-analytic models of galaxy formation. The cosmological model that we use reproduces the Fundamental Metallicity Relation recently discovered for the SDSS galaxies, whereby the metallicity decreases with increasing Star Formation Rate for galaxies of a given stellar mass. We select host galaxies housing pockets of gas-particles, young and with different thresholds in metallicities, that can be sites of LRGB events, according to the collapsar model. The simulated samples are compared with 18 observed LGRB hosts in the aim at discriminating whether the metallicity is a primary parameter. We find that a threshold in metallicity for the LGRB progenitors, within the model galaxies, is not necessary in order to reproduce the observed distribution of host metallicities. The low metallicities of observed LGRB hosts is a consequence of the high star formation environment. The star formation rate appears to be the primary parameter to generate a burst event. Finally, we show that only a few LGRBs are observed in massive, highly extincted galaxies, while these galaxies are expected to produce many such events. We identify these missing events with the fraction of dark LGRBs.
قيم البحث
اقرأ أيضاً
We present the results from a large near-infrared spectroscopic survey with Subaru/FMOS (textit{FastSound}) consisting of $sim$ 4,000 galaxies at $zsim1.4$ with significant H$alpha$ detection. We measure the gas-phase metallicity from the [N~{sc ii}]
$lambda$6583/H$alpha$ emission line ratio of the composite spectra in various stellar mass and star-formation rate bins. The resulting mass-metallicity relation generally agrees with previous studies obtained in a similar redshift range to that of our sample. No clear dependence of the mass-metallicity relation with star-formation rate is found. Our result at $zsim1.4$ is roughly in agreement with the fundamental metallicity relation at $zsim0.1$ with fiber aperture corrected star-formation rate. We detect significant [S~{sc ii}]$lambdalambda$6716,6731 emission lines from the composite spectra. The electron density estimated from the [S~{sc ii}]$lambdalambda$6716,6731 line ratio ranges from 10 -- 500 cm$^{-3}$, which generally agrees with that of local galaxies. On the other hand, the distribution of our sample on [N~{sc ii}]$lambda$6583/H$alpha$ vs. [S~{sc ii}]$lambdalambda$6716,6731/H$alpha$ is different from that found locally. We estimate the nitrogen-to-oxygen abundance ratio (N/O) from the N2S2 index, and find that the N/O in galaxies at $zsim1.4$ is significantly higher than the local values at a fixed metallicity and stellar mass. The metallicity at $zsim1.4$ recalculated with this N/O enhancement taken into account decreases by 0.1 -- 0.2 dex. The resulting metallicity is lower than the local fundamental metallicity relation.
We use $sim$83,000 star-forming galaxies at $0.04<z<0.3$ from the Sloan Digital Sky Survey to study the so-called fundamental metallicity relation (FMR) and report on the disappearance of its anti-correlation between metallicity and star formation ra
te (SFR) when using the new metallicity indicator recently proposed by Dopita et al. In this calibration, metallicity is primarily sensitive to the emission line ratio [NII]$lambda$6584 / [SII]$lambdalambda$6717, 6731 that is insensitive to dilution by pristine infalling gas that may drive the FMR anti-correlation with SFR. Therefore, we conclude that the apparent disappearance of the FMR (using this new metallicity indicator) does not rule out its existence.
The fundamental metallicity relation (FMR) is a postulated correlation between galaxy stellar mass, star formation rate (SFR), and gas-phase metallicity. At its core, this relation posits that offsets from the mass-metallicity relation (MZR) at a fix
ed stellar mass are correlated with galactic SFR. In this Letter, we quantify the timescale with which galactic SFRs and metallicities evolve using hydrodynamical simulations. We find that Illustris and IllustrisTNG predict that galaxy offsets from the star formation main sequence and MZR evolve over similar timescales, are often anti-correlated in their evolution, evolve with the halo dynamical time, and produce a pronounced FMR. In fact, for a FMR to exist, the metallicity and SFR must evolve in an anti-correlated sense which requires that they evolve with similar time variability. In contrast to Illustris and IllustrisTNG, we speculate that the SFR and metallicity evolution tracks may become decoupled in galaxy formation models dominated by globally-bursty SFR histories, which could weaken the FMR residual correlation strength. This opens the possibility of discriminating between bursty and non-bursty feedback models based on the strength and persistence of the FMR -- especially at high redshift.
Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell
1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red sequence lenticular galaxies and blue cloud galaxies, low mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally-driven gas flows toward the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red sequence or blue cloud galaxies, at fixed stellar mass, with location within the cluster.
Recent results have suggested that the well known mass-metallicity relation has a strong dependence on the star formation rate, to the extent that a three dimensional `fundamental metallicity relation exists which links the three parameters with mini
mal scatter. In this work, we use a sample of 4253 local galaxies observed in atomic hydrogen from the ALFALFA survey to demonstrate, for the first time, that a similar fundamental relation (the HI-FMR) also exists between stellar mass, gas-phase metallicity, and HI mass. This latter relation is likely more fundamental, driving the relation between metallicity, SFR and mass. At intermediate masses, the behaviour of the gas fundamental metallicity relation is very similar to that expressed via the star formation rate. However, we find that the dependence of metallicity on HI content persists to the highest stellar masses, in contrast to the `saturation of metallicity with SFR. It is interesting to note that the dispersion of the relation is very low at intermediate stellar masses (9< log(M*/Msun) <11), suggesting that in this range galaxies evolve smoothy, in an equilibrium between gas inflow, outflow and star formation. At high and low stellar masses, the scatter of the relation is significantly higher, suggesting that merging events and/or stochastic accretion and star formation may drive galaxies outside the relation. We also assemble a sample of galaxies observed in CO. However, due to a small sample size, strong selection bias, and the influence of a metallicity-dependent CO/H2 conversion factor, the data are insufficient to test any influence of molecular gas on metallicity.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
