Luca Ciotti - Academia.edu (original) (raw)
Papers by Luca Ciotti
The astrophysical journal, Jul 29, 2016
We present new photometry of the dwarf irregular galaxy DDO68, one of the most metal-poor and le... more We present new photometry of the dwarf irregular galaxy DDO68, one of the most metal-poor and least massive dwarfs, located in the Lynx-Cancer Void. The images were acquired with the Large Binocular Telescope in the g and r passbands and show unequivocally that DDO68 has previously unknown stellar streams related to the accretion of at least two smaller companions: a flea with smaller fleas biting it, to put it in Jonathan Swift's words (from Jonathan Swift's On Poetry: a Rhapsody: So, naturalists observe, a flea/has smaller fleas that on him prey/and these have smaller still to bite em/and so proceed ad infinitum). Our data provide direct observational evidence of multiple galaxy merging occurring at very low galactic mass scales. We present the results of an N-body simulation of the interaction of three dwarf galaxies that reproduce well the main morphological features of DDO68.
arXiv (Cornell University), Apr 12, 2023
It has been suggested that the observed flat rotation curves of disk galaxies can be a peculiar e... more It has been suggested that the observed flat rotation curves of disk galaxies can be a peculiar effect of General Relativity (GR) rather than evidence for the presence of dark matter (DM) halos in Newtonian gravity. In Ciotti (2022) the problem has been quantitatively addressed by using the well known weak-field, low-velocity gravitomagnetic limit of GR, for realistic exponential baryonic (stellar) disks. As expected, the resulting GR and Newtonian rotation curves are indistinguishable, with GR corrections at all radii of the order of v 2 /c 2 ≈ 10 −6. Here we list some astrophysical problems that must be faced if the existence of DM halos is attributed to a misinterpretation of weak field effects of GR.
Monthly Notices of the Royal Astronomical Society, Nov 20, 2019
The Smallest Scale of Hierarchy (SSH) survey is an ongoing strategic large program at the Large B... more The Smallest Scale of Hierarchy (SSH) survey is an ongoing strategic large program at the Large Binocular Telescope, aimed at the detection of faint stellar streams and satellites around 45 late-type dwarf galaxies located in the Local Universe within 10 Mpc. SSH exploits the wide-field, deep photometry provided by the Large Binocular Cameras in the two wide filters g and r. This paper describes the survey, its goals, and the observational and data reduction strategies. We present preliminary scientific results for five representative cases (UGC 12613, NGC 2366, UGC 685, NGC 5477 and UGC 4426) covering the whole distance range spanned by the SSH targets. We reach a surface brightness limit as faint as µ(r) ∼ 31 mag arcsec −2 both for targets closer than 4−5 Mpc, which are resolved into individual stars, and for more distant targets through the diffuse light. Our analysis reveals the presence of extended low surface brightness stellar envelopes around the dwarfs, reaching farther out than what traced by the integrated light, and as far out as, or even beyond, the observed H I disk. Stellar streams, arcs, and peculiar features are detected in some cases, indicating possible perturbation, accretion, or merging events. We also report on the discovery of an extreme case of Ultra Diffuse Galaxy (µ g (0) = 27.9 mag/arcsec 2) in the background of one of our targets, to illustrate the power of the survey in revealing extremely low surface brightness systems.
Monthly Notices of the Royal Astronomical Society, Feb 9, 2017
We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β) objects ... more We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z = 6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their de-lensed half light radii (R e) are between 16 to 140 pc, the stellar masses are 1 − 20 × 10 6 M , the magnitudes are m U V = 28.8 − 31.4 (−17 < M U V < −15) and specific star formation rates can be as large as ∼ 800 Gyr −1. Multiple images of these systems are widely separated in the sky (up to 50) and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σ v 20 km s −1 , implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with de-lensed M U V −15.3 (m U V 31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with de-lensed m U V 32, a stellar mass of 0.5 ×10 6 M and a star formation rate of 0.06 M yr −1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the restframe optical and near-infrared properties of such low-luminosity high−z objects.
Monthly Notices of the Royal Astronomical Society, Nov 12, 2022
We study the formation and evolution of elliptical galaxies and how they suppress star formation ... more We study the formation and evolution of elliptical galaxies and how they suppress star formation and maintain it quenched. A one-zone chemical model which follows in detail the time evolution of gas mass and its chemical abundances during the active and passive evolution, is adopted. The model includes both gas infall and outflow as well as detailed stellar nucleosynthesis. Elliptical galaxies with different infall masses, following a down-sizing in star formation scenario, are considered. In the chemical evolution simulation we include a novel calculation of the feedback processes. We include heating by stellar wind, core-collapse SNe, Type Ia SNe (usually not highlighted in galaxy formation simulations) and AGN feedback. The AGN feedback is a novelty in this kind of models and is computed by considering a Bondi-Eddington limited accretion onto the central supermassive black hole. We successfully reproduce several observational features, such as the [ /Fe] ratios increasing with galaxy mass, mass-metallicity, M BH − and M BH − M * relations. Moreover, we show that stellar feedback and in particular Type Ia SNe, has a main role in maintaining quenched the star formation after the occurrence of the main galactic wind, especially in low-mass ellipticals. For larger systems, the contribution from AGN to thermal energy of gas appears to be necessary. However, the effect of the AGN on the development of the main galactic wind is negligible, unless an unreasonable high AGN efficiency or an extremely low stellar feedback are assumed. We emphasize the important role played by Type Ia SNe in the energy budget of early-type galaxies.
Symposium - International Astronomical Union, 1996
arXiv (Cornell University), Jan 28, 2015
High resolution 2D hydrodynamical simulations describing the evolution of the hot ISM in axisymme... more High resolution 2D hydrodynamical simulations describing the evolution of the hot ISM in axisymmetric two-component models of early-type galaxies well reproduced the observed trends of the X-ray luminosity (L X) and temperature (T X) with galaxy shape and rotation, however they also revealed the formation of an exceedingly massive cooled gas disc in rotating systems. In a follow-up of this study, here we investigate the effects of star formation in the disc, including the consequent injection of mass, momentum and energy in the pre-existing interstellar medium. It is found that subsequent generations of stars originate one after the other in the equatorial region; the mean age of the new stars is > 5 Gyr, and the adopted recipe for star formation can reproduce the empirical Kennicutt-Schmidt relation. The results of the previous investigation without star formation, concerning L X and T X of the hot gas, and their trends with galactic shape and rotation, are confirmed. At the same time, the consumption of most of the cold gas disc into new stars leads to more realistic final systems, whose cold gas mass and star formation rate agree well with those observed in the local universe. In particular, our models could explain the observation of kinematically aligned gas in massive, fast-rotating early-type galaxies.
We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar... more We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar orbits inside cluster Elliptical galaxies (Es). In particular we discuss, with the aid of a simple numerical model, the possibility that collisionless stellar evaporation from elliptical galaxies is an effective mechanism for the production of the recently discovered intracluster stellar populations (ISP). A preliminary investigation, based on very idealized galaxy density profiles (Ferrers density distributions), showed that over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near equilibrium configurations in the CTF are comparable to stellar orbital times in the external galaxy regions. Here we extend our previous study to more realistic galaxy density profiles, in particular by adopting a triaxial Hernquist model.
Astronomy and Astrophysics, May 1, 1997
Following a first paper on this subject (Ciotti 1991, hereafter Paper I), we study the dynamical ... more Following a first paper on this subject (Ciotti 1991, hereafter Paper I), we study the dynamical properties of spherical galaxies with surface luminosity profile described by the R 1/m-law, in which a variable degree of orbital anisotropy is allowed. The parameter m for the present models covers the range [1, 10]. For these models we study the self-consistently generated phase-space distribution function (DF), and we derive-as a function of m-the minimum value of the anisotropy radius for the model consistency (i.e., in order to have a nowhere negative DF). Then we study the region in the parameter space where the R 1/m models are likely to be stable against radialorbit instability, and we compare its size with that of the larger region corresponding to the consistency requirement. For stable anisotropic models the spatial and projected velocity dispersion profiles are obtained solving the Jeans equation, and compared to those of the globally isotropic case, already discussed in Paper I. The relevance of the results in connection with the fundamental plane (FP) of elliptical galaxies is pointed out: the effect on the projected velocity dispersion due to the maximum orbital anisotropy allowed by the stability requirement is well within the FP thickness, and so no fine-tuning for anisotropy is required. Finally, the velocity profiles are constructed as a function of the projected radius and for various degrees of anisotropy, and their deviations from a gaussian discussed.
The Astrophysical Journal, Feb 10, 2010
By using high-resolution 1D hydrodynamical simulations, we investigate the effects of purely mech... more By using high-resolution 1D hydrodynamical simulations, we investigate the effects of purely mechanical feedback from super massive black holes (SMBHs) in the evolution of elliptical galaxies for a broad range of feedback efficiencies and compare the results to four major observational constraints. In particular, we focus on 1) the central black hole to stellar mass ratio of the host galaxy, 2) the lifetime of the luminous quasar phase, 3) the mass of stars formed in the host galaxy within the last Gyr, and 4) the X-ray luminosity of the hot diffuse
Monthly Notices of the Royal Astronomical Society, Sep 1, 1996
Proceedings of the International Astronomical Union, May 1, 2018
A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the... more A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the stellar and total mass, for a sample of nearby early-type galaxies (ETGs), is used to investigate the origin of the hot gas, via a comparison with the results of hydrodynamical simulations of the ISM evolution for a large set of isolated ETGs. After the epoch of major galaxy formation (after z 2), the ISM is replenished by stellar mass losses and SN ejecta, at the rate predicted by stellar evolution, and is depleted by star formation; it is heated by the thermalization of stellar motions, SNe explosions and the mechanical (from winds) and radiative AGN feedback. The models agree well with the observed relations, even for the largely different L X values at the same mass, thanks to the sensitivity of the gas flow to many galaxy properties; this holds for models including AGN feedback, and those without. Therefore, the mass input from the stellar population is able to account for a major part of the observed L X ; and AGN feedback, while very important to maintain massive ETGs in a time-averaged quasi-steady state, keeping low star formation and the black hole mass, does not dramatically alter the gas content originating in stellar recycled material. These conclusions are based on theoretical predictions for the stellar population contributions in mass and energy, and on a self-consistent modeling of AGN feedback.
The Astrophysical Journal, Mar 29, 2018
A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the... more A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the stellar and total mass for a sample of nearby early-type galaxies (ETGs) is used to investigate the origin of the hot gas, via a comparison with the results of hydrodynamical simulations of the ISM evolution for a large set of isolated ETGs. After the epoch of major galaxy formation (after z;2), the ISM is replenished by stellar mass losses and SN ejecta, at the rate predicted by stellar evolution, and is depleted by star formation; it is heated by the thermalization of stellar motions, SNe explosions, and the mechanical (from winds) and radiative AGN feedback. The models agree well with the observed relations, even for the largely different L X values at the same mass, thanks to the sensitivity of the gas flow to many galaxy properties; this holds for models including AGN feedback, and those without. Therefore, the mass input from the stellar population is able to account for a major part of the observed L X ; and AGN feedback, while very important to maintain massive ETGs in a time-averaged quasi-steady state, keeping low star formation and the black hole mass, does not dramatically alter the gas content originating in stellar recycled material. These conclusions are based on theoretical predictions for the stellar population contributions in mass and energy, and on a self-consistent modeling of AGN feedback.
arXiv (Cornell University), Mar 7, 2023
The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the ... more The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of MACER, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that the inflow gas hardly enters but is blocked beyond ∼ 20 kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominant contributed by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of ≳ 20. This increase is not because of the additional gas supply by the inflow but due to the increase of gas density and pressure in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of ∼ 5 and ∼ 1000, respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.
The Astrophysical Journal, Apr 22, 2019
We add a suite of chemical abundances to the MACER (Massive AGN Controlled Ellipticals Resolved) ... more We add a suite of chemical abundances to the MACER (Massive AGN Controlled Ellipticals Resolved) 2D code, by solving 12 additional continuity equations for H, He, C, N, O, Ne, Mg, Si, S, Ca, Fe and Ni respectively with sources from AGB stars and supernovae of type Ia and II with metal yields based on standard stellar physics. New stars, formed in Toomre unstable circumnuclear disks (of a size 150 parsec), are assumed to have a top-heavy initial mass function with a power index of 1.65. The metal dilution effects due to cosmic accretion are also included. With the high resolution of few parsecs in central regions, resolved black hole accretion and AGN feedback, we can track the metal enrichment, transportation and dilution throughout the modeled massive elliptical galaxy of velocity dispersion ∼ 280 km/s. We retrieve the chemical composition of the BAL winds launched by the central AGN, synthesize the X-ray features of the hot ISM, and find that (1) the simulated metallicity in the BAL winds could be up to ∼ 8Z , while that of the hot ISM in the host galaxy is ∼ 2.3Z , matching well with SDSS observations of BLR gas; (2) the X-ray emitting hot gas is metal enriched with a typical value ∼ 2.5Z ; (3) the circumunuclear cold gas disk, where the metals are condensed, further enriched and recycled, plays a critical role in the metal enrichment; (4) the black hole accretion ratė M BH linearly correlates with the star formation rateṀ + in the circumnuclear disk, i.e,Ṁ + ∼ 7.7Ṁ BH , but lagged in time by roughly 10 6 years.
Astronomy and Astrophysics, Jun 22, 2004
We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar... more We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar orbits inside cluster Elliptical galaxies (Es). In particular we discuss, with the aid of a simple numerical model, the possibility that collisionless stellar evaporation from elliptical galaxies is an effective mechanism for the production of the recently discovered intracluster stellar populations (ISP). A preliminary investigation, based on very idealized galaxy density profiles (Ferrers density distributions), showed that over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near equilibrium configurations in the CTF are comparable to stellar orbital times in the external galaxy regions. Here we extend our previous study to more realistic galaxy density profiles, in particular by adopting a triaxial Hernquist model.
Springer eBooks, 1996
A recent analysis of the relationship between optical and X-ray properties for the Einstein sampl... more A recent analysis of the relationship between optical and X-ray properties for the Einstein sample of early-type galaxies has revealed that S0 galaxies have lower mean X-ray luminosity L X per unit optical luminosity L B than do ellipticals. In the same analysis, signi cant correlations are found between the X-ray properties and the axial ratios, such that the roundest systems have the highest L X =L B ; this trend holds also for either Es or S0s alone (Eskridge et al. 1995a,b). The systematic X-ray underluminosity of S0s with respect to Es could be explained with a higher heat input or with a lower gravitational energy (all per unit gas mass), at xed L B. The gravitational energy could be lower because of their higher rotation, which decreases the e ective potential, or their di erent mass distribution. These possibilities are examined here, by considering their rôle in the global energy budget of the hot gas ows in earlytype galaxies. The e ect of the attening of the mass distribution is investigated with galaxy models described by the Miyamoto-Nagai potential{density pair, to which a dark matter halo of various shapes is added. For these two-component models the analytical expressions of the gravitational energy, and the stellar kinetic energy associated with various relative amounts of random motions and rotational streaming, are given. It is found that rotation cannot produce a change in the ow phase of the hot gas, independently of the galaxy shape and the presence of dark matter. The e ect of attening instead can be substantial in reducing the binding energy of the hot gas. Thus S0s and possibly non spherical Es are less able to retain a signi cant halo of hot gas than rounder Es of the same L B .
Proceedings of the International Astronomical Union, May 1, 2019
We present a significantly improved version of our numerical code JASMINE, that can now solve the... more We present a significantly improved version of our numerical code JASMINE, that can now solve the Jeans equations for axisymmetric models of stellar systems, composed of an arbitrary number of stellar populations, a Dark Matter halo, and a central Black Hole. The stellar components can have different structural (density profile, flattening, mass, scale length), dynamical (rotational support, velocity dispersion anisotropy), and population (age, metallicity, Initial Mass Function, mass-to-light ratio) properties. These models, when combined with observations, will allow to investigate important issues, such as quantifying the systematic effects of IMF variations, of mass-to-light ratio gradients, and of different stellar kinematic components (e.g. counter rotating disks, kinematically decoupled cores) on luminosity-weighted properties. The developed analytical and numerical framework aims at modeling Early-Type Galaxies, but it can also be applied to dwarf Spheroidal galaxies and Globular Clusters.
The astrophysical journal, Jul 29, 2016
We present new photometry of the dwarf irregular galaxy DDO68, one of the most metal-poor and le... more We present new photometry of the dwarf irregular galaxy DDO68, one of the most metal-poor and least massive dwarfs, located in the Lynx-Cancer Void. The images were acquired with the Large Binocular Telescope in the g and r passbands and show unequivocally that DDO68 has previously unknown stellar streams related to the accretion of at least two smaller companions: a flea with smaller fleas biting it, to put it in Jonathan Swift's words (from Jonathan Swift's On Poetry: a Rhapsody: So, naturalists observe, a flea/has smaller fleas that on him prey/and these have smaller still to bite em/and so proceed ad infinitum). Our data provide direct observational evidence of multiple galaxy merging occurring at very low galactic mass scales. We present the results of an N-body simulation of the interaction of three dwarf galaxies that reproduce well the main morphological features of DDO68.
arXiv (Cornell University), Apr 12, 2023
It has been suggested that the observed flat rotation curves of disk galaxies can be a peculiar e... more It has been suggested that the observed flat rotation curves of disk galaxies can be a peculiar effect of General Relativity (GR) rather than evidence for the presence of dark matter (DM) halos in Newtonian gravity. In Ciotti (2022) the problem has been quantitatively addressed by using the well known weak-field, low-velocity gravitomagnetic limit of GR, for realistic exponential baryonic (stellar) disks. As expected, the resulting GR and Newtonian rotation curves are indistinguishable, with GR corrections at all radii of the order of v 2 /c 2 ≈ 10 −6. Here we list some astrophysical problems that must be faced if the existence of DM halos is attributed to a misinterpretation of weak field effects of GR.
Monthly Notices of the Royal Astronomical Society, Nov 20, 2019
The Smallest Scale of Hierarchy (SSH) survey is an ongoing strategic large program at the Large B... more The Smallest Scale of Hierarchy (SSH) survey is an ongoing strategic large program at the Large Binocular Telescope, aimed at the detection of faint stellar streams and satellites around 45 late-type dwarf galaxies located in the Local Universe within 10 Mpc. SSH exploits the wide-field, deep photometry provided by the Large Binocular Cameras in the two wide filters g and r. This paper describes the survey, its goals, and the observational and data reduction strategies. We present preliminary scientific results for five representative cases (UGC 12613, NGC 2366, UGC 685, NGC 5477 and UGC 4426) covering the whole distance range spanned by the SSH targets. We reach a surface brightness limit as faint as µ(r) ∼ 31 mag arcsec −2 both for targets closer than 4−5 Mpc, which are resolved into individual stars, and for more distant targets through the diffuse light. Our analysis reveals the presence of extended low surface brightness stellar envelopes around the dwarfs, reaching farther out than what traced by the integrated light, and as far out as, or even beyond, the observed H I disk. Stellar streams, arcs, and peculiar features are detected in some cases, indicating possible perturbation, accretion, or merging events. We also report on the discovery of an extreme case of Ultra Diffuse Galaxy (µ g (0) = 27.9 mag/arcsec 2) in the background of one of our targets, to illustrate the power of the survey in revealing extremely low surface brightness systems.
Monthly Notices of the Royal Astronomical Society, Feb 9, 2017
We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β) objects ... more We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z = 6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their de-lensed half light radii (R e) are between 16 to 140 pc, the stellar masses are 1 − 20 × 10 6 M , the magnitudes are m U V = 28.8 − 31.4 (−17 < M U V < −15) and specific star formation rates can be as large as ∼ 800 Gyr −1. Multiple images of these systems are widely separated in the sky (up to 50) and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σ v 20 km s −1 , implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with de-lensed M U V −15.3 (m U V 31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with de-lensed m U V 32, a stellar mass of 0.5 ×10 6 M and a star formation rate of 0.06 M yr −1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the restframe optical and near-infrared properties of such low-luminosity high−z objects.
Monthly Notices of the Royal Astronomical Society, Nov 12, 2022
We study the formation and evolution of elliptical galaxies and how they suppress star formation ... more We study the formation and evolution of elliptical galaxies and how they suppress star formation and maintain it quenched. A one-zone chemical model which follows in detail the time evolution of gas mass and its chemical abundances during the active and passive evolution, is adopted. The model includes both gas infall and outflow as well as detailed stellar nucleosynthesis. Elliptical galaxies with different infall masses, following a down-sizing in star formation scenario, are considered. In the chemical evolution simulation we include a novel calculation of the feedback processes. We include heating by stellar wind, core-collapse SNe, Type Ia SNe (usually not highlighted in galaxy formation simulations) and AGN feedback. The AGN feedback is a novelty in this kind of models and is computed by considering a Bondi-Eddington limited accretion onto the central supermassive black hole. We successfully reproduce several observational features, such as the [ /Fe] ratios increasing with galaxy mass, mass-metallicity, M BH − and M BH − M * relations. Moreover, we show that stellar feedback and in particular Type Ia SNe, has a main role in maintaining quenched the star formation after the occurrence of the main galactic wind, especially in low-mass ellipticals. For larger systems, the contribution from AGN to thermal energy of gas appears to be necessary. However, the effect of the AGN on the development of the main galactic wind is negligible, unless an unreasonable high AGN efficiency or an extremely low stellar feedback are assumed. We emphasize the important role played by Type Ia SNe in the energy budget of early-type galaxies.
Symposium - International Astronomical Union, 1996
arXiv (Cornell University), Jan 28, 2015
High resolution 2D hydrodynamical simulations describing the evolution of the hot ISM in axisymme... more High resolution 2D hydrodynamical simulations describing the evolution of the hot ISM in axisymmetric two-component models of early-type galaxies well reproduced the observed trends of the X-ray luminosity (L X) and temperature (T X) with galaxy shape and rotation, however they also revealed the formation of an exceedingly massive cooled gas disc in rotating systems. In a follow-up of this study, here we investigate the effects of star formation in the disc, including the consequent injection of mass, momentum and energy in the pre-existing interstellar medium. It is found that subsequent generations of stars originate one after the other in the equatorial region; the mean age of the new stars is > 5 Gyr, and the adopted recipe for star formation can reproduce the empirical Kennicutt-Schmidt relation. The results of the previous investigation without star formation, concerning L X and T X of the hot gas, and their trends with galactic shape and rotation, are confirmed. At the same time, the consumption of most of the cold gas disc into new stars leads to more realistic final systems, whose cold gas mass and star formation rate agree well with those observed in the local universe. In particular, our models could explain the observation of kinematically aligned gas in massive, fast-rotating early-type galaxies.
We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar... more We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar orbits inside cluster Elliptical galaxies (Es). In particular we discuss, with the aid of a simple numerical model, the possibility that collisionless stellar evaporation from elliptical galaxies is an effective mechanism for the production of the recently discovered intracluster stellar populations (ISP). A preliminary investigation, based on very idealized galaxy density profiles (Ferrers density distributions), showed that over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near equilibrium configurations in the CTF are comparable to stellar orbital times in the external galaxy regions. Here we extend our previous study to more realistic galaxy density profiles, in particular by adopting a triaxial Hernquist model.
Astronomy and Astrophysics, May 1, 1997
Following a first paper on this subject (Ciotti 1991, hereafter Paper I), we study the dynamical ... more Following a first paper on this subject (Ciotti 1991, hereafter Paper I), we study the dynamical properties of spherical galaxies with surface luminosity profile described by the R 1/m-law, in which a variable degree of orbital anisotropy is allowed. The parameter m for the present models covers the range [1, 10]. For these models we study the self-consistently generated phase-space distribution function (DF), and we derive-as a function of m-the minimum value of the anisotropy radius for the model consistency (i.e., in order to have a nowhere negative DF). Then we study the region in the parameter space where the R 1/m models are likely to be stable against radialorbit instability, and we compare its size with that of the larger region corresponding to the consistency requirement. For stable anisotropic models the spatial and projected velocity dispersion profiles are obtained solving the Jeans equation, and compared to those of the globally isotropic case, already discussed in Paper I. The relevance of the results in connection with the fundamental plane (FP) of elliptical galaxies is pointed out: the effect on the projected velocity dispersion due to the maximum orbital anisotropy allowed by the stability requirement is well within the FP thickness, and so no fine-tuning for anisotropy is required. Finally, the velocity profiles are constructed as a function of the projected radius and for various degrees of anisotropy, and their deviations from a gaussian discussed.
The Astrophysical Journal, Feb 10, 2010
By using high-resolution 1D hydrodynamical simulations, we investigate the effects of purely mech... more By using high-resolution 1D hydrodynamical simulations, we investigate the effects of purely mechanical feedback from super massive black holes (SMBHs) in the evolution of elliptical galaxies for a broad range of feedback efficiencies and compare the results to four major observational constraints. In particular, we focus on 1) the central black hole to stellar mass ratio of the host galaxy, 2) the lifetime of the luminous quasar phase, 3) the mass of stars formed in the host galaxy within the last Gyr, and 4) the X-ray luminosity of the hot diffuse
Monthly Notices of the Royal Astronomical Society, Sep 1, 1996
Proceedings of the International Astronomical Union, May 1, 2018
A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the... more A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the stellar and total mass, for a sample of nearby early-type galaxies (ETGs), is used to investigate the origin of the hot gas, via a comparison with the results of hydrodynamical simulations of the ISM evolution for a large set of isolated ETGs. After the epoch of major galaxy formation (after z 2), the ISM is replenished by stellar mass losses and SN ejecta, at the rate predicted by stellar evolution, and is depleted by star formation; it is heated by the thermalization of stellar motions, SNe explosions and the mechanical (from winds) and radiative AGN feedback. The models agree well with the observed relations, even for the largely different L X values at the same mass, thanks to the sensitivity of the gas flow to many galaxy properties; this holds for models including AGN feedback, and those without. Therefore, the mass input from the stellar population is able to account for a major part of the observed L X ; and AGN feedback, while very important to maintain massive ETGs in a time-averaged quasi-steady state, keeping low star formation and the black hole mass, does not dramatically alter the gas content originating in stellar recycled material. These conclusions are based on theoretical predictions for the stellar population contributions in mass and energy, and on a self-consistent modeling of AGN feedback.
The Astrophysical Journal, Mar 29, 2018
A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the... more A recent determination of the relationships between the X-ray luminosity of the ISM (L X) and the stellar and total mass for a sample of nearby early-type galaxies (ETGs) is used to investigate the origin of the hot gas, via a comparison with the results of hydrodynamical simulations of the ISM evolution for a large set of isolated ETGs. After the epoch of major galaxy formation (after z;2), the ISM is replenished by stellar mass losses and SN ejecta, at the rate predicted by stellar evolution, and is depleted by star formation; it is heated by the thermalization of stellar motions, SNe explosions, and the mechanical (from winds) and radiative AGN feedback. The models agree well with the observed relations, even for the largely different L X values at the same mass, thanks to the sensitivity of the gas flow to many galaxy properties; this holds for models including AGN feedback, and those without. Therefore, the mass input from the stellar population is able to account for a major part of the observed L X ; and AGN feedback, while very important to maintain massive ETGs in a time-averaged quasi-steady state, keeping low star formation and the black hole mass, does not dramatically alter the gas content originating in stellar recycled material. These conclusions are based on theoretical predictions for the stellar population contributions in mass and energy, and on a self-consistent modeling of AGN feedback.
arXiv (Cornell University), Mar 7, 2023
The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the ... more The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of MACER, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that the inflow gas hardly enters but is blocked beyond ∼ 20 kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominant contributed by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of ≳ 20. This increase is not because of the additional gas supply by the inflow but due to the increase of gas density and pressure in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of ∼ 5 and ∼ 1000, respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts.
The Astrophysical Journal, Apr 22, 2019
We add a suite of chemical abundances to the MACER (Massive AGN Controlled Ellipticals Resolved) ... more We add a suite of chemical abundances to the MACER (Massive AGN Controlled Ellipticals Resolved) 2D code, by solving 12 additional continuity equations for H, He, C, N, O, Ne, Mg, Si, S, Ca, Fe and Ni respectively with sources from AGB stars and supernovae of type Ia and II with metal yields based on standard stellar physics. New stars, formed in Toomre unstable circumnuclear disks (of a size 150 parsec), are assumed to have a top-heavy initial mass function with a power index of 1.65. The metal dilution effects due to cosmic accretion are also included. With the high resolution of few parsecs in central regions, resolved black hole accretion and AGN feedback, we can track the metal enrichment, transportation and dilution throughout the modeled massive elliptical galaxy of velocity dispersion ∼ 280 km/s. We retrieve the chemical composition of the BAL winds launched by the central AGN, synthesize the X-ray features of the hot ISM, and find that (1) the simulated metallicity in the BAL winds could be up to ∼ 8Z , while that of the hot ISM in the host galaxy is ∼ 2.3Z , matching well with SDSS observations of BLR gas; (2) the X-ray emitting hot gas is metal enriched with a typical value ∼ 2.5Z ; (3) the circumunuclear cold gas disk, where the metals are condensed, further enriched and recycled, plays a critical role in the metal enrichment; (4) the black hole accretion ratė M BH linearly correlates with the star formation rateṀ + in the circumnuclear disk, i.e,Ṁ + ∼ 7.7Ṁ BH , but lagged in time by roughly 10 6 years.
Astronomy and Astrophysics, Jun 22, 2004
We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar... more We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar orbits inside cluster Elliptical galaxies (Es). In particular we discuss, with the aid of a simple numerical model, the possibility that collisionless stellar evaporation from elliptical galaxies is an effective mechanism for the production of the recently discovered intracluster stellar populations (ISP). A preliminary investigation, based on very idealized galaxy density profiles (Ferrers density distributions), showed that over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near equilibrium configurations in the CTF are comparable to stellar orbital times in the external galaxy regions. Here we extend our previous study to more realistic galaxy density profiles, in particular by adopting a triaxial Hernquist model.
Springer eBooks, 1996
A recent analysis of the relationship between optical and X-ray properties for the Einstein sampl... more A recent analysis of the relationship between optical and X-ray properties for the Einstein sample of early-type galaxies has revealed that S0 galaxies have lower mean X-ray luminosity L X per unit optical luminosity L B than do ellipticals. In the same analysis, signi cant correlations are found between the X-ray properties and the axial ratios, such that the roundest systems have the highest L X =L B ; this trend holds also for either Es or S0s alone (Eskridge et al. 1995a,b). The systematic X-ray underluminosity of S0s with respect to Es could be explained with a higher heat input or with a lower gravitational energy (all per unit gas mass), at xed L B. The gravitational energy could be lower because of their higher rotation, which decreases the e ective potential, or their di erent mass distribution. These possibilities are examined here, by considering their rôle in the global energy budget of the hot gas ows in earlytype galaxies. The e ect of the attening of the mass distribution is investigated with galaxy models described by the Miyamoto-Nagai potential{density pair, to which a dark matter halo of various shapes is added. For these two-component models the analytical expressions of the gravitational energy, and the stellar kinetic energy associated with various relative amounts of random motions and rotational streaming, are given. It is found that rotation cannot produce a change in the ow phase of the hot gas, independently of the galaxy shape and the presence of dark matter. The e ect of attening instead can be substantial in reducing the binding energy of the hot gas. Thus S0s and possibly non spherical Es are less able to retain a signi cant halo of hot gas than rounder Es of the same L B .
Proceedings of the International Astronomical Union, May 1, 2019
We present a significantly improved version of our numerical code JASMINE, that can now solve the... more We present a significantly improved version of our numerical code JASMINE, that can now solve the Jeans equations for axisymmetric models of stellar systems, composed of an arbitrary number of stellar populations, a Dark Matter halo, and a central Black Hole. The stellar components can have different structural (density profile, flattening, mass, scale length), dynamical (rotational support, velocity dispersion anisotropy), and population (age, metallicity, Initial Mass Function, mass-to-light ratio) properties. These models, when combined with observations, will allow to investigate important issues, such as quantifying the systematic effects of IMF variations, of mass-to-light ratio gradients, and of different stellar kinematic components (e.g. counter rotating disks, kinematically decoupled cores) on luminosity-weighted properties. The developed analytical and numerical framework aims at modeling Early-Type Galaxies, but it can also be applied to dwarf Spheroidal galaxies and Globular Clusters.