Formation and evolution of elliptical galaxies and QSO activity

Friaça, Amâncio César Santos; Terlevich, Elena

doi:10.1046/j.1365-8711.1998.01626.x

Cited by 65 publications

(79 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is generally assumed that the significantly different timescales of the release of -elements and iron to the interstellar medium results in a time delay on the order of $1 Gyr in the iron enrichment. However, recent studies by Matteucci (1994), Friaça & Terlevich (1998), and Matteucci & Recchi (2001) indicate that this delay may be $0.2-0.6 Gyr for elliptical galaxies. Detecting Fe ii emission at high redshift comparable to the relative strength observed in quasars at lower redshift indicates that the formation of the stars that had released the iron occurred $0.3-0.8 Gyr earlier in the quasar host galaxy.…”

Section: Introductionmentioning

confidence: 94%

Feii/MgiiEmission‐Line Ratio in High‐Redshift Quasars

Dietrich

Hamann

Appenzeller³

et al. 2003

ApJ

128

146

View full text Add to dashboard Cite

We present results of the analysis of near-infrared spectroscopic observations of six high-redshift quasars (ze4), emphasizing the measurement of the ultraviolet Fe ii/Mg ii emission-line strength to estimate the beginning of intense star formation in the early universe. To investigate the evolution of the Fe ii/Mg ii ratio over a wider range in cosmic time, we measured this ratio for composite quasar spectra that cover a redshift range 0dzd5 with nearly constant luminosity, as well as for those that span $6 orders of magnitude in luminosity. A detailed comparison of the high-redshift quasar spectra with those of low-redshift quasars with comparable luminosity shows essentially the same Fe ii/Mg ii emission ratios and very similar continuum and line spectral properties, i.e., a lack of evolution of the relative iron-to-magnesium abundance of the gas in bright quasars since z ' 5. Current nucleosynthesis and stellar evolution models predict that -elements such as magnesium are produced in massive stars ending in Type II supernovae, while iron is formed predominantly in Type Ia supernovae with intermediate-mass progenitors. This results in an iron enrichment delay of $0.2-0.6 Gyr. We conclude that intense star formation activity in the host galaxies of ze4 quasars must have started already at an epoch corresponding to z f ' 6-9, when the age of the universe was $0.5 Gyr (H 0 ¼ 72 km s À1 Mpc À1 , M ¼ 0:3, Ã ¼ 0:7). This epoch corresponds well to the reionization era of the universe.

show abstract

Section: Introductionmentioning

confidence: 94%

Feii/MgiiEmission‐Line Ratio in High‐Redshift Quasars

Dietrich

Hamann

Appenzeller³

et al. 2003

ApJ

128

146

View full text Add to dashboard Cite

show abstract

“…A more general puzzle about abundances inferred from quasar BLRs is that they appear to require very high metallicities, Z > ∼ 5Z⊙ (e.g., Dietrich et al 2003, Nagao et al 2006. It is somewhat challenging to reach these metallicities with global star formation models (e.g., Hamann & Ferland 1993, Friaca & Terlevich 1998, Romano et al 2002, leading to an alternative picture of star formation associated with the outer, self-gravitating parts of the accretion flow (e.g., Collin & Zahn 1999, Wang et al 2011. BLR metallicity estimates use the steady increase of nitrogen relative to oxygen and carbon as the overall metallicity increases (Hamann & Ferland 1993).…”

Section: Nitrogen Rich Quasars and Tdesmentioning

confidence: 99%

Abundance anomalies in tidal disruption events

Kochanek

2016

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

The ∼ 10% of tidal disruption events (TDEs) due to stars more massive than M * > ∼ M ⊙ should show abundance anomalies due to stellar evolution in helium, carbon and nitrogen, but not oxygen. Helium is always enhanced, but only by up to ∼ 25% on average because it becomes inaccessible once it is sequestered in the high density core as the star leaves the main sequence. However, portions of the debris associated with the disrupted core of a main sequence star can be enhanced in helium by factors of 2-3 for debris at a common orbital period. These helium abundance variations may be a contributor to the observed diversity of hydrogen and helium line strengths in TDEs. A still more striking anomaly is the rapid enhancement of nitrogen and the depletion of carbon due to the CNO cycle -stars with M * > ∼ M ⊙ quickly show an increase in their average N/C ratio by factors of 3-10. Because low mass stars evolve slowly and high mass stars are rare, TDEs showing high N/C will almost all be due to 1-2M ⊙ stars disrupted on the main sequence. Like helium, portions of the debris will show still larger changes in C and N, and the anomalies decline as the star leaves the main sequence. The enhanced [N/C] abundance ratio of these TDEs provides the first natural explanation for the rare, nitrogen rich quasars and also explains the strong nitrogen emission seen in ultraviolet spectra of ASASSN-14li.

show abstract

“…The chemodynamical model is based on the model of galactic chemical evolution of Friaça & Terlevich (1998), which combines a multi-zone chemical evolution solver and a hydrodynamical code. In the model, a single massive dark halo hosts baryonic gas that can form stars.…”

Section: Introductionmentioning

confidence: 99%

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

Friaça

Barbuy

2017

A&A

View full text Add to dashboard Cite

Context. Galactic bulge abundances can be best understood as indicators of bulge formation and nucleosynthesis processes by comparing them with chemo-dynamical evolution models. Aims. The aim of this work is to study the abundances of alpha-elements in the Galactic bulge, including a revision of the oxygen abundance in a sample of 56 bulge red giants. Methods. Literature abundances for O, Mg, Si, Ca and Ti in Galactic bulge stars are compared with chemical evolution models. For oxygen in particular, we reanalysed high-resolution spectra obtained using FLAMES+UVES on the Very Large Telescope, now taking each star's carbon abundances, derived from CI and C 2 lines, into account simultaneously.Results. We present a chemical evolution model of alpha-element enrichment in a massive spheroid that represents a typical classical bulge evolution. The code includes multi-zone chemical evolution coupled with hydrodynamics of the gas. Comparisons between the model predictions and the abundance data suggest a typical bulge formation timescale of 1-2 Gyr. The main constraint on the bulge evolution is provided by the O data from analyses that have taken the C abundance and dissociative equilibrium into account. Mg, Si, Ca and Ti trends are well reproduced, whereas the level of overabundance critically depends on the adopted nucleosynthesis prescriptions.

show abstract

Formation and evolution of elliptical galaxies and QSO activity

Cited by 65 publications

References 62 publications

Feii/MgiiEmission‐Line Ratio in High‐Redshift Quasars

Feii/MgiiEmission‐Line Ratio in High‐Redshift Quasars

Abundance anomalies in tidal disruption events

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

Contact Info

Product

Resources

About