The kinematics of σ-drop bulges from spectral synthesis modelling of a hydrodynamical simulation
Elisa Portaluri, Victor P. Debattista, Maximillian Fabricius, David R. Cole, Enrico M. Corsini, Niv Drory, Andrew Rowe, Lorenzo Morelli, Alessandro Pizzella, Elena Dalla Bonta'
A minimum in stellar velocity dispersion is often observed in the central regions of disc galaxies. To investigate the origin of this feature, known as a σ-drop, we analyse the stellar kinematics of a high-resolution N-body + smooth particle hydrodynamical simulation, which models the secular evolution of an unbarred disc galaxy. We compared the intrinsic mass-weighted kinematics to the recovered luminosity-weighted ones. The latter were obtained by analysing synthetic spectra produced by a new code, SYNTRA, that generates synthetic spectra by assigning a stellar population synthesis model to each star particle based on its age and metallicity. The kinematics were derived from the synthetic spectra as in real spectra to mimic the kinematic analysis of real galaxies. We found that the recovered luminosity-weighted kinematics in the centre of the simulated galaxy are biased to higher rotation velocities and lower velocity dispersions due to the presence of young stars in a thin and kinematically cool disc, and are ultimately responsible for the σ-drop.
We present dynamical models of the star-forming galaxy NGC 5474 based on $N$-body hydrodynamical numerical simulations. We investigate the possible origin of the compact round stellar structure, generally interpreted as the bulge of the galaxy, but unusually off-set by $\simeq1$ kpc in projection from the visual and the kinematic centres of both the star and the gas discs. We argue that it is very unlikely that the putative bulge is in a co-planar orbit in the disc plane, showing that such a configuration would be hardly compatible with its smooth and regular spatial distribution, and, in case…
We compare galaxy morphology predicted by the Illustris hydrodynamical simulation and a semi-analytic model (SAM) grafted in the halo merger trees from the Illustris-Dark matter simulation. Morphology is classified according to the luminous profile and the kinematic bulge-to-total ratio for Illustris galaxy, and the bulge-to-total stellar mass ratio for SAM galaxy. For late-type galaxies in the Illustris catalogue, most of their counterparts in the SAM model have the same type, and the consistency between two models is higher for lower mass galaxies. For early-type (ET) galaxies in Illustris, …
Until a decade ago, galaxy formation simulations were unable to simultaneously reproduce the observed angular momentum (AM) of galaxy disks and bulges. Improvements in the interstellar medium and stellar feedback modelling, together with advances in computational capabilities, have allowed the current generation of cosmological galaxy formation simulations to reproduce the diversity of AM and morphology that is observed in local galaxies. In this review I discuss where we currently stand in this area from the perspective of hydrodynamical simulations, specifically how galaxies gain their AM, a…
We present an image-based method for comparing the structural properties of galaxies produced in hydrodynamical simulations to real galaxies in the Sloan Digital Sky Survey. The key feature of our work is the introduction of extensive observational realism, such as object crowding, noise and viewing angle, to the synthetic images of simulated galaxies, so that they can be fairly compared to real galaxy catalogs. We apply our methodology to the dust-free synthetic image catalog of galaxies from the Illustris simulation at $z=0$, which are then fit with bulge+disc models to obtain morphological …
The interpretive power of the newest generation of large-volume hydrodynamical simulations of galaxy formation rests upon their ability to reproduce the observed properties of galaxies. In this second paper in a series, we employ bulge+disc decompositions of realistic dust-free galaxy images from the Illustris simulation in a consistent comparison with galaxies from the Sloan Digital Sky Survey (SDSS). Examining the size-luminosity relations of each sample, we find that galaxies in Illustris are roughly twice as large and $0.7$ magnitudes brighter on average than galaxies in the SDSS. The tren…
We analyse the kinematics of $\sim 2000$ giant stars in the direction of the Galactic bulge, extracted from the Gaia-ESO survey in the region $-10^\circ \lesssim \ell \lesssim 10^\circ$ and $-11^\circ \lesssim b \lesssim -3^\circ$. We find distinct kinematic trends in the metal rich ($\mathrm{[M/H]}>0$) and metal poor ($\mathrm{[M/H]}<0$) stars in the data. The velocity dispersion of the metal-rich stars drops steeply with latitude, compared to a flat profile in the metal-poor stars, as has been seen previously. We argue that the metal-rich stars in this region are mostly on orbits that suppor…
We show for the first time, that a fully cosmological hydrodynamical simulation can reproduce key properties of the innermost region of the Milky Way. Our high resolution simulation matches the profile and kinematics of the Milky Way's boxy/peanut-shaped bulge, and hence we can use it to reconstruct and understand the bulge assembly. In particular, the age dependence of the X-shape morphology of the simulated bulge parallels the observed metallicity dependent split in the red clump stars of the inner Galaxy. We use this feature to derive an observational metric that allows us to quantify when …
In the era of precision cosmology and ever-improving cosmological simulations, a better understanding of different galaxy components such as bulges and discs will give us new insight into galactic formation and evolution. Based on the fact that the stellar populations of the constituent components of galaxies differ by their dynamical properties, we develop two simple models for galaxy decomposition using the IllustrisTNG cosmological hydrodynamical simulation. The first model uses a single dynamical parameter and can distinguish 4 components: thin disc, thick disc, counter-rotating disc and b…
Correlations between black holes and their host galaxies provide insight into what drives black hole-host co-evolution. We use the Meraxes semi-analytic model to investigate the growth of black holes and their host galaxies from high redshift to the present day. Our modelling finds no significant evolution in the black hole-bulge and black hole-total stellar mass relations out to a redshift of 8. The black hole-total stellar mass relation has similar but slightly larger scatter than the black hole-bulge relation, with the scatter in both decreasing with increasing redshift. In our modelling th…
The formation and evolutionary history of M31 are closely related to its dynamical structures, which remain unclear due to its high inclination. Gas kinematics could provide crucial evidence for the existence of a rotating bar in M31. Using the position-velocity diagram of [OIII] and HI, we are able to identify clear sharp velocity jump (shock) features with a typical amplitude over 100 km/s in the central region of M31 (4.6 kpc X 2.3 kpc, or 20 arcmin X 10 arcmin). We also simulate gas morphology and kinematics in barred M31 potentials and find that the bar-induced shocks can produce velocity…
We study the galactic bulges in the Auriga simulations, a suite of thirty cosmological magneto-hydrodynamical zoom-in simulations of late-type galaxies in Milky Way-sized dark matter haloes performed with the moving-mesh code AREPO. We aim to characterize bulge formation mechanisms in this large suite of galaxies simulated at high resolution in a fully cosmological context. The bulges of the Auriga galaxies show a large variety in their shapes,sizes and formation histories. According to observational classification criteria, such as Sersic index and degree of ordered rotation, the majority of …
Bulgeless Evolution And the Rise of Discs (BEARD) III. A numerical simulation view of satellites around Milky-Way analogues
Universidad de La Laguna（拉各拉大学）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Donostia International Physics Centre (DIPC)（多诺斯蒂亚国际物理中心）；Universidad de Córdoba（科尔多瓦大学）
The stellar populations in the inner kiloparsecs of the Milky Way (MW) show complex kinematical and chemical structures. The origin and evolution of these structures is still under debate. Here we study the central region of a fully cosmological hydrodynamical simulation of a disk galaxy that reproduces key properties of the inner kiloparsecs of the MW: it has a boxy morphology and shows an overall rotation and dispersion profile in agreement with observations. We use a clustering algorithm on stellar kinematics to identify a number of discrete kinematic components: a high- and low-spin disk, …
We present detailed morphological, photometric, and stellar-kinematic analyses of the central regions of two massive, early-type barred galaxies with nearly identical large-scale morphologies. Both have large, strong bars with prominent inner photometric excesses that we associate with boxy/peanut-shaped (B/P) bulges; the latter constitute ~ 30% of the galaxy light. Inside its B/P bulge, NGC 4608 has a compact, almost circular structure (half-light radius R_e approx. 310 pc, Sérsic n = 2.2) we identify as a classical bulge, amounting to 12.1% of the total light, along with a nuclear star clust…
We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those `green valley' objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of bulges was a late event that induced the sSFRs of massive galaxies to drop in a slow downfall, and thus the main sequence to bend. We have studied in detail a sample of 10 galaxies at $0.45<z<1$ with secure SFR from Herschel, deep Keck optical spectr…
Galaxies exhibit coherent alignments with local structure in the Universe. This effect, called Intrinsic Alignments (IA), is an important contributor to the systematic uncertainties for wide-field weak lensing surveys. On cosmological distance scales, intrinsic shape alignments have been observed in red galaxies, which are usually bulge-dominated; while blue galaxies, which are mostly disc-dominated, exhibit shape alignments consistent with a null detection. However, disc-dominated galaxies typically consist of two prominent structures: disc and bulge. Since the bulge component has similar pro…
The properties of central stellar knots embedded in galactic bulges of CIELO simulations
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Instituto de Astrofísica, Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学天体物理研究所）；Centro de AstroIngeniería, Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学天文工程中心）；Instituto de Astronomía y Física del Espacio, CONICET-UBA（空间天文与物理研究所，阿根廷国家科学研究委员会-布宜诺斯艾利斯大学）
We explore the chemodynamical properties of a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in simulations, which form boxy/peanut (b/p) bulges, and compare these to the Milky Way (MW). We show that the Auriga galaxies which best reproduce the chemodynamical properties of stellar populations in the MW bulge have quiescent merger histories since redshift $z\sim3.5$: their last major merger occurs at $t_{\rm lookback}>12\,\rm Gyrs$, while subsequent mergers have a stellar mass ratio of $\leq$1:20, suggesting an upper limit of a few percent for the mass ratio of…
Quenched galaxies are often observed to contain a strong bulge component. The key question is whether this reflects a causal connection - can star formation be quenched dynamically by bulges or the spheroids of early-type galaxies? We systematically investigate the impact of these morphological components on star formation, by performing a suite of hydrodynamical simulations of isolated galaxies containing a spheroid. We vary the bulge mass and scale radius, while the total initial stellar, halo and gas mass are kept constant, with a gas fraction of 5 per cent. In addition, we consider two dif…
We present gas and stellar kinematics of a high-resolution zoom-in cosmological chemodynamical simulation, which fortuitously captures the formation and evolution of a star-forming barred spiral galaxy, from redshift $z\sim3$ to $z\sim2$ at the peak of the cosmic star formation rate. The galaxy disc grows by accreting gas and substructures from the environment. The spiral pattern becomes fully organised when the gas settles from a thick (with vertical dispersion $σ_{v} >$ 50 km/s) to a thin ($σ_{v} \sim 25$ km/s) disc component in less than 1 Gyr. Our simulated disc galaxy also has a central X…
We study the formation and evolution of ring galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations. We use the largest reference model Ref-L100N1504, a cubic cosmological volume of 100 comoving megaparsecs on a side, to identify and characterise these systems through cosmic time. The number density of ring galaxies in EAGLE is in broad agreement with the observations. The vast majority of ring galaxies identified in EAGLE (83 per cent) have an interaction origin, i.e., form when one or more companion galaxies drop-through a disk galaxy. The remainder (17…
In a complete sample of local 14-195 keV selected AGNs and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10-150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, 8 AGNs and 5 inactive galaxies. The stellar velocity fields show a disk-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of g…
We investigate correlations between different physical properties of star-forming galaxies in the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) cosmological hydrodynamical simulation suite over the redshift range $0\le z\le 4.5$. A principal component analysis reveals that neutral gas fraction ($f_{\rm gas, neutral}$), stellar mass ($M_{\rm stellar}$) and star formation rate (SFR) account for most of the variance seen in the population, with galaxies tracing a two-dimensional, nearly flat, surface in the three-dimensional space of $f_{\rm gas, neutral}-M_{\rm stellar}-\rm…
The MUSE TIMER Survey has obtained high signal and high spatial resolution integral-field spectroscopy data of the inner $\sim6\times6$ kpc of 21 nearby massive disc galaxies. This allows studies of the stellar kinematics of the central regions of massive disc galaxies that are unprecedented in spatial resolution. We confirm previous predictions from numerical and hydrodynamical simulations of the effects of bars and inner bars on stellar and gaseous kinematics, and also identify box/peanuts via kinematical signatures in mildly and moderately inclined galaxies, including a box/peanut in a face…
The SMUGGLE-Ring project: Bar and bulge effects on nuclear disk and ring formation
Università di Bologna（博洛尼亚大学）；INAF, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学台）；Universität Potsdam（波茨坦大学）；Université Côte d’Azur, Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS（蔚蓝海岸大学蔚蓝海岸天文台拉格朗日实验室）；Seoul National University（首尔大学）；Massachusetts Institute of Technology（麻省理工学院）
Galaxy properties are known to correlate most tightly with the galaxy effective stellar velocity dispersion $σ_{\rm e}$. Here we look for {\em additional} trends at fixed $σ_{\rm e}$ using 1339 galaxies ($M_\ast \gtrsim 6\times10^9$ M$_\odot$) with different morphologies in the MaNGA (DR14) sample with integral-field spectroscopy data. We focus on the gradients ($γ_{\rm rms} \equiv σ(R_{\rm e}/4)/σ_{\rm e}$) of the stellar root-mean-square velocity ($V_{\rm rms} \equiv \sqrt{V^2 + σ^2}$), which we show traces the total mass density gradient $γ_{\rm tot}$ derived from dynamical models and, more…
We present a two-dimensional multi-component photometric decomposition of 404 galaxies from the CALIFA Data Release 3. They represent all possible galaxies with no clear signs of interaction and not strongly inclined in the final CALIFA data release. Galaxies are modelled in the g, r, and i SDSS images including, when appropriate, a nuclear point source, bulge, bar, and an exponential or broken disc component. We use a human-supervised approach to determine the optimal number of structures to be included in the fit. The dataset, including the photometric parameters of the CALIFA sample, is rel…
Galaxies host a wide array of internal stellar components, which need to be decomposed accurately in order to understand their formation and evolution. While significant progress has been made with recent integral-field spectroscopic surveys of nearby galaxies, much can be learned from analyzing the large sets of realistic galaxies now available through state-of-the-art hydrodynamical cosmological simulations. We present an unsupervised machine learning algorithm, named auto-GMM, based on Gaussian mixture models, to isolate intrinsic structures in simulated galaxies based on their kinematic ph…
A hydrodynamical CLONE of the Virgo cluster: II. Confronting observed and synthetic galaxy population twins in a dense environment
Univ. Lille, CNRS, Centrale Lille, UMR 9189 CRIStAL（里尔大学）；Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale（巴黎萨克雷大学）；University of Birmingham School of Physics and Astronomy（伯明翰大学）；Institut d’Astrophysique de Paris, UMR 7095, Sorbonne Université, CNRS（索邦大学）；Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574（里昂大学）；Universidad Autónoma de Madrid（马德里自治大学）；International Centre for Radio Astronomy Research, University of Western Australia（西澳大利亚大学）
We quantify the impact that a variety of galactic and environmental properties have on the quenching of star formation. We collate a sample of $\sim$ 400,000 central and $\sim$ 100,000 satellite galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Specifically, we consider central velocity dispersion ($σ_{c}$), stellar, halo, bulge and disk mass, local density, bulge-to-total ratio, group-centric distance and galaxy-halo mass ratio. We develop and apply a new statistical technique to quantify the impact on the quenched fraction ($f_{\rm Quench}$) of varying one parameter, whil…
