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There is mounting evidence that the stellar initial mass function (IMF) could extend much beyond the canonical Mi ~100, Msun limit, but the impact of such hypothesis on the chemical enrichment of galaxies still remains to be clarified. We…

Astrophysics of Galaxies · Physics 2021-06-30 S. Goswami , A. Slemer , P. Marigo , A. Bressan , L. Silva , M. Spera , L. Boco , V. Grisoni , L. Pantoni , A. Lapi

Recent observations of active galactic nuclei (AGNs) have shown a high Fe~II/Mg~II line-flux ratio in their broad-line regions, nearly independent of redshift up to $z \gtrsim 6$. The high flux ratio requires rapid production of iron in…

Astrophysics of Galaxies · Physics 2022-03-14 Daisuke Toyouchi , Kohei Inayoshi , Miho N. Ishigaki , Nozomu Tominaga

Recent studies proposed that cosmic rays (CR) are a key ingredient in setting the conditions for star formation, thanks to their ability to alter the thermal and chemical state of dense gas in the UV-shielded cores of molecular clouds. In…

Astrophysics of Galaxies · Physics 2018-02-14 Fabio Fontanot , Gabriella De Lucia , Lizhi Xie , Michaela Hirschmann , Gustavo Bruzual , Stephane Charlot

The stellar initial mass function (IMF) seems to be variable and not universal, as argued in the literature in the last three decades. Several relations among the low-mass end of the IMF slope and other stellar population, photometric or…

Astrophysics of Galaxies · Physics 2021-01-13 C. E. Barbosa , C. Spiniello , M. Arnaboldi , L. Coccato , M. Hilker , T. Richtler

Recent spatially-resolved observations of massive early-type galaxies (ETGs) have uncovered evidence for radial gradients of the stellar initial mass function (IMF), ranging from super-Salpeter IMFs in the centre to Milky Way-like beyond…

Astrophysics of Galaxies · Physics 2018-11-06 Christopher Barber , Joop Schaye , Robert A. Crain

Systematic variations of the IMF in early-type galaxies, and their connection with possible drivers such as velocity dispersion or metallicity, have been much debated in recent years. Strong lensing over galaxy scales combined with…

Astrophysics of Galaxies · Physics 2016-04-27 Dominik Leier , Ignacio Ferreras , Prasenjit Saha , Stéphane Charlot , Gustavo Bruzual , Francesco La Barbera

The Initial Mass Function (IMF) for massive galaxies can be constrained by combining stellar dynamics with strong gravitational lensing. However, this method is limited by degeneracies between the density profile of dark matter and the…

The stellar mass distribution in star-forming regions, stellar clusters and associations, the Initial Mass Function (IMF), appears to be invariant across different star-forming environments, and is consistent with the IMF observed in the…

Astrophysics of Galaxies · Physics 2024-12-03 Sunder S. K. Singh-Bal , George A. Blaylock-Squibbs , Richard J. Parker , Simon P. Goodwin

One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to constrain different star formation models that predict the IMF. However, those…

Astrophysics of Galaxies · Physics 2018-04-25 David Guszejnov , Philip F. Hopkins , Xiangcheng Ma

Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 Crescenzo Tortora , Aaron J. Romanowsky , Nicola R. Napolitano

We present a uniform analysis of the stellar initial mass function (IMF) from integrated light spectroscopy of 15 compact stellar systems (11 globular clusters in M31 and 4 ultra compact dwarfs in the Virgo cluster, UCDs) and two brightest…

Some ultra-compact dwarf galaxies have large dynamical mass to light (M/L) ratios and also appear to contain an overabundance of LMXB sources, and some Milky Way globular clusters have a low concentration and appear to have a deficit of…

Astrophysics of Galaxies · Physics 2020-03-18 Pavel Kroupa

Motivated by the observed bottom-light initial mass function (IMF) in faint dwarfs, we study how a metallicity-dependent IMF affects the feedback budget and observables of an ultra-faint dwarf galaxy. We model the evolution of a low-mass…

The expected metal enrichment of the intra-cluster medium (ICM) and the partition of metals between cluster galaxies and the hot ICM depends on the stellar Initial Mass Function (IMF). The choice of the IMF in simulations of clusters has…

Astrophysics · Physics 2007-05-23 L. Portinari

The molecular gas, H$_2$, that fuels star formation in galaxies is difficult to observe directly. As such, the ratio of $L_{\rm IR}$ to $L^\prime_{\rm CO}$ is an observational estimation of the star formation rate compared with the amount…

We describe the use of our chemical evolution model to reproduce the abundance patterns observed in a catalog of elliptical galaxies from the SDSS DR4. The model assumes ellipticals form by fast gas accretion, and suffer a strong burst of…

Astrophysics of Galaxies · Physics 2018-01-10 Carlo Maria De Masi , Francesca Matteucci , Fiorenzo Vincenzo

The initial mass function (IMF) of stars is a key quantity affecting almost every field of astrophysics, yet it remains unclear what physical mechanisms determine it. We present the first runs of the STARFORGE project, using a new numerical…

Studies of the broad emission-line regions (BLRs) in quasars have revealed solar or higher enrichment levels up to the highest redshifts. In combination with the presence of large amounts of dust in QSOs at $z$ about 6, this implies that…

Astrophysics · Physics 2009-11-10 Aparna Venkatesan , Raffaella Schneider , Andrea Ferrara

The epoch of reionization and formation of first stars are inter-linked topics that are of considerable interest. We use a simplified approach for studying formation of stars in collapsed haloes, and the resulting ionization of the…

Cosmology and Nongalactic Astrophysics · Physics 2010-05-07 J. S. Bagla , Girish Kulkarni , T. Padmanabhan

It is usually assumed that the stellar initial mass function (IMF) takes a universal form and that there exists a direct mapping between this and the distribution of natal core masses (the core mass function, CMF). The IMF and CMF have been…