Galaxy interactions can have an important effect in a galaxy's evolution. Cosmological models predict a large number of small satellites around galaxies. It is important to study the effect that these small satellites can have on the host. The present work explores the effect of small N-body spherical satellites with total mass ratios in the range approx 1:1000-1:100 in inducing gas flows to the central regions of a disc galaxy with late-type morphology resembling the Milky Way. Two model galaxies are considered: barred and non-barred models; the latter one is motivated in order to isolate and understand better the effects of the satellite. Several circular and non-circular orbits are explored, considering both prograde and retrogade orientations. We show that satellites with such small mass ratios can still produce observable distortions in the gas and stellar components of the galaxy. In terms of gas flows, the prograde circular orbits are more favourable for producing gas flows, where in some cases up to $60% of the gas of the galaxy is driven to the central region. We find, hence, that small satellites can induce significant gas flows to the central regions of a disc galaxy, which is relevant in the context of fuelling active galactic nuclei.
We model the infall of a 2e5 Msun satellite galaxy on to the inner 200 parsec of our Galaxy, to test whether the satellite could perturb the gas previously on stable orbits in the central molecular zone (CMZ), as proposed by Lang et al. (2013). This process would have driven a large gas inflow around 10 Myr ago, necessary to explain the past high accretion rate onto the super-massive black hole, and the presence of young stars in the inner parsecs of the Galaxy. Our hydrodynamical simulations show a much smaller inflow of gas, not sufficient to produce the aforementioned effects.
Satellite Metallicity Enhancement I: Suppressed Star Formation, Stellar Mass Loss, and Enriched Inflow of DESI and EAGLE Galaxies around Massive Clusters
State Key Laboratory of Dark Matter Physics & Tsung-Dao Lee Institute, Shanghai Jiao Tong University（暗物质物理国家重点实验室暨李政道研究所，上海交通大学）；Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交大物理与天文学院天文学系）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Department of Physics, Boston University（波士顿大学物理系）；Department of Physics & Astronomy, University College London（伦敦大学学院物理与天文系）；Instituto de Física, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理研究所）
Using the EAGLE suite of simulations, we demonstrate that both cold gas stripping {\it and} starvation of gas inflow play an important role in quenching satellite galaxies across a range of stellar and halo masses, $M_{\star}$ and $M_{200}$. By quantifying the balance between gas inflows, outflows, and star formation rates, we show that even at $z=2$, only $\approx30\%$ of satellite galaxies are able to maintain equilibrium or grow their reservoir of cool gas - compared to $\approx50\%$ of central galaxies at this redshift. We find that the number of orbits completed by a satellite is a very g…
In this letter we investigate the effect of boxy/peanut (b/p) bulges on bar-induced gas inflow to the central kiloparsec, which plays a crucial role on the evolution of disc galaxies. We carry out hydrodynamic gas response simulations in realistic barred galaxy potentials, including or not the geometry of a b/p bulge, to investigate the amount of gas inflow induced in the different models. We find that b/p bulges can reduce the gas inflow rate to the central kiloparsec by more than an order of magnitude, which leads to a reduction in the amount of gas available in the central regions. We also …
The baryon cycle of galaxies is a dynamic process involving the intake, consumption and ejection of vast quantities of gas. In contrast, the conventional picture of satellite galaxies has them methodically turning a large gas reservoir into stars until this reservoir is forcibly removed due to external ram pressure. This picture needs revision. Our modern understanding of the baryon cycle suggests that in some regimes the simple interruption of the fresh gas supply may quench satellite galaxies long before stripping events occur, a process we call overconsumption. We compile measurements from …
Numerical models of gas inflow towards a supermassive black hole (SMBH) show that star formation may occur in such an environment through the growth of a gravitationally unstable gas disc. We consider the effect of nuclear activity on such a scenario. We present the first three-dimensional grid-based radiative hydrodynamic simulations of direct collisions between infalling gas streams and a $4 \times 10^6~\text{M}_\odot$ SMBH, using ray-tracing to incorporate radiation consistent with an active galactic nucleus (AGN). We assume inflow masses of $ \approx 10^5~\text{M}_\odot$ and explore radiat…
Stellar bars are a common feature in massive disc galaxies. On a theoretical ground, the response of gas to a bar is generally thought to cause nuclear starbursts and, possibly, AGN activity once the perturbed gas reaches the central super-massive black hole. By means of high resolution numerical simulations we detail the purely dynamical effects that a forming bar exerts on the gas of an isolated disc galaxy. The galaxy is initially unstable to the formation of non-axisymmetric structures, and within 1 Gyr it develops spiral arms that eventually evolve into a central stellar bar on kpc scale.…
Observations of galaxies in the local Universe have shown that both the ionized gas and the stars of satellites are more metal-rich than of equally massive centrals. To gain insight into the connection between this metallicity enhancement and other differences between centrals and satellites, such as their star formation rates, gas content, and growth history, we study the metallicities of >3600 galaxies with M_star > 10^10 M_sun in the cosmological hydrodynamical EAGLE 100 Mpc `Reference' simulation, including ~1500 in the vicinity of galaxy groups and clusters (M_200 >= 10^13 M_sun). The sim…
The main challenge for understanding the fuelling of supermassive black holes in active galactic nuclei is not to account for the source of fuel, but rather to explain its delivery from the boundaries of the black hole sphere of influence (10-100 pc) down to sub-parsec scales. In this work, we report on a series of numerical experiments aimed at exploring in further depth our model of "overlapping inflow events" as catalysts for rapid accretion, seeding a turbulent field in the infalling gas. We initially set a gaseous shell in non-equilibrium rotation around a supermassive black hole. After i…
Disc galaxies show a large morphological diversity with varying contribution of three major structural components; thin discs, thick discs, and central bulges. Dominance of bulges increases with the galaxy mass (Hubble sequence) whereas thick discs are more prominent in lower mass galaxies. Because galaxies grow with the accretion of matter, this observed variety should reflect diversity in accretion history. On the basis of the prediction by the cold-flow theory for galactic gas accretion and inspired by the results of previous studies, we put a hypothesis that associates different accretion …
The submillimeter galaxy (SMG) HERMES J105751.1+573027 (hereafter HLock01) at z = 2.9574 +/- 0.0001 is one of the brightest gravitationally lensed sources discovered in the Herschel Multi-tiered Extragalactic Survey. Apart from the high flux densities in the far-infrared, it is also extremely bright in the rest-frame ultraviolet (UV), with a total apparent magnitude m_UV = 19.7 mag. We report here deep spectroscopic observations with the Gran Telescopio Canarias of the optically bright lensed images of HLock01. Our results suggest that HLock01 is a merger system composed of the Herschel-select…
An analytical chemical evolution model is constructed to investigate the radial distribution of gas-phase and stellar metallicity for star-forming galaxies. By means of the model, the gas-phase and stellar metallicity can be obtained from the stellar-to-gas mass ratio. Both the gas inflow and outflow processes play an important role in building the final gas-phase metallicity, and there exists degeneracy effect between the gas inflow and outflow rates for star-forming galaxies. On the other hand, stellar metallicity is more sensitive to the gas outflow rate than to the gas inflow rate, and thi…
Gas inflow feeds galaxies with low metallicity gas from the cosmic web, sustaining star formation across the Hubble time. We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of the Halpha emission line from zoom-in AMR cosmological simulations of galaxies with stellar masses of $M \simeq 10^9 $Msun at redshifts z=2-7. In $\sim$50\% of the cases at redshifts lower than 4, the gas inflow gives rise to star-forming, Halpha-bright, off-centre clumps. Most of these clumps have gas metallicities, weighted by Halph…
We study the gas inflow rate ($ζ_{\rm inflow}$) and outflow rate ($ζ_{\rm outflow}$) evolution of local Milky Way-mass star-forming galaxies (SFGs) since $z=1.3$. The stellar mass growth history of Milky Way-mass progenitor SFGs is inferred from the evolution of the star formation rate (SFR)$-$stellar mass ($M_{\ast}$) relation, and the gas mass ($M_{\rm gas}$) is derived using the recently established gas scaling relations. With the $M_{\ast}+M_{\rm gas}$ growth curve, the net inflow rate $κ$ is quantified at each cosmic epoch. At $z\sim 1.3$, $κ$ is comparable with the SFR, whereas it rapidl…
We report on the discovery of cool gas inflow toward six star-forming galaxies with redshifts z ~ 0.35 - 1. Analysis of MgII and FeII resonance-line absorption in Keck/LRIS spectroscopy of this sample reveals velocity shifts of 80 - 200 km/s and equivalent widths for inflowing gas of >~ 0.6 Ang in five of the six objects. The host galaxies exhibit a wide range in star formation rates (SFR ~ 1 - 40 M_sun/yr) and have stellar masses similar to that of the Milky Way (log M_*/M_sun ~ 9.6 - 10.5). Imaging from the Hubble Space Telescope Advanced Camera for Surveys indicates that five of the six gal…
We use the 30 simulations of the Auriga Project to estimate the temporal dependency of the inflow, outflow and net accretion rates onto the discs of Milky Way-like galaxies. The net accretion rates are found to be similar for all galaxies at early times, increasing rapidly up to $\sim 10~\mathrm{M}_\odot \, \mathrm{yr}^{-1}$. After $\sim 6~\mathrm{Gyr}$ of evolution, however, the net accretion rates are diverse: in most galaxies, these exhibit an exponential-like decay, but some systems instead present increasing or approximately constant levels up to the present time. An exponential fit to th…
We present a low-redshift (z=0.029) Damped Lyman-alpha (DLA) system in the spectrum of a background Quasi-Stellar Object (QSO). The DLA is associated with an interacting galaxy pair within a galaxy group. We detected weak Lyman-alpha emission centered at the absorption trough of the DLA. The emission was likely tracing the neutral HI reservoir around the galaxies in the interacting pair, which scattered the Lyman-alpha generated by star formation within those galaxies. We also found that the interacting pair is enveloped by a large HI cloud with $M(HI)=2\times 10^{10}M_{\odot}$. We discovered …
The high-ionization lines of the broad-line region (BLR) of thermal active galactic nuclei (AGNs) show blueshifts of a few hundred km/s to several thousand km/sec with respect to the low-ionization lines. This has long been thought to be due to the high-ionization lines of the BLR arising in a wind of which the far side of the outflow is blocked from our view by the accretion disc. Evidence for and against the disc-wind model is discussed. The biggest problem for the model is that velocity-resolved reverberation mapping repeatedly fails to show the expected kinematic signature of outflow of th…
We model the kinematics of the high- and intermediate- velocity clouds (HVCs and IVCs) observed in absorption towards a sample of 55 Galactic halo stars with accurate distance measurements. We employ a simple model of a thick disc whose main free parameters are the gas azimuthal, radial and vertical velocities ($v_ϕ$, $v_{\rm R}$ and $v_{\rm z}$), and apply it to the data by fully accounting for the distribution of the observed features in the distance-velocity space. We find that at least two separate components are required to reproduce the data. A scenario where the HVCs and the IVCs are tr…
The role of gas in the mass assembly at the nuclei of galaxies is still subject to some uncertainty. Stellar nuclear discs bridge the gap between the large-scale galaxy and the central massive objects that reside there. Using a high resolution simulation of a galaxy forming out of gas cooling and settling into a disc, we study the formation and properties of nuclear discs. Gas, driven to the centre by a bar, settles into a rotating star-forming nuclear disc (ND). This ND is thinner, younger, kinematically cooler, and more metal-rich than the surrounding bar. The ND is elliptical and orthogonal…
Spiral galaxies comprise three major structural components; thin discs, thick discs, and central bulges. Relative dominance of these components is known to correlate with the total mass of the galaxy, and produces a remarkable morphological variety of spiral galaxies. Although there are many formation scenarios regarding individual components, no unified theory exists which explains this systematic variation. The cold-flow hypothesis predicts that galaxies grow by accretion of cold gas from cosmic webs (cold accretion) when their mass is below a certain threshold, whereas in the high-mass regi…
Peering down the barrel with DESI DR2: 10 000+ inflows at $z$ < 0.6 reveal how galaxies accrete cold gas
Aix Marseille Univ, CNRS, CNES, LAM（艾克斯马赛大学）；Department of Physics & Astronomy, University College London（伦敦大学学院物理与天文系）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Department of Physics and Astronomy, Siena University（锡耶纳大学物理与天文系）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo（东京大学宇宙物质研究前沿中心）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Department of Physics, Boston University（波士顿大学物理系）；Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano（米兰大学阿尔多·蓬特罗莫利物理系）；INAF-Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）
Giant radio galaxies provide important clues into the life cycles and triggering mechanisms of radio jets. With large-scale jets spanning 1.8 Mpc, ESO 422-G028 ($z = 0.038$) is a giant radio galaxy that also exhibits signs of restarted jet activity in the form of pc-scale jets. We present a study of the spatially-resolved stellar and gas properties of ESO 422-G028 using optical integral field spectroscopy from the WiFeS spectrograph. In addition to the majority $\sim 13\,\rm Gyr$ old stellar population, ESO 422-G028 exhibits a much younger ($\lesssim 10\,\rm Myr$ old) component with an estimat…
Satellite compaction pathways: environmental drivers shaping dwarf galaxy corpulence in the TNG50 simulation
Instituto de Astronomia, Geofísica e Ciências Atmosféricas (Universidade de São Paulo)（天文、地球物理与大气科学研究所（圣保罗大学））；Institut d’Astrophysique de Paris (UMR 7095: CNRS & Sorbonne Université)（巴黎天体物理研究所（CNRS与索邦大学联合研究单位7095））
The Galactic bar plays a critical role in the evolution of the Milky Way's Central Molecular Zone (CMZ), driving mass inward toward the Galactic Center via gas flows known as dust lanes. To explore the interaction between the CMZ and the dust lanes, we run hydrodynamic simulations in AREPO, modeling the potential of the Milky Way's bar in the absence of gas self-gravity and star formation physics, and we study the flows of mass using Monte Carlo tracer particles. We estimate the efficiency of the inflow via the dust lanes, finding that only about a third (30$\pm$12%) of the dust lanes' mass in…
One of the greatest issues in modelling black hole fuelling is our lack of understanding of the processes by which gas loses angular momentum and falls from galactic scales down to the nuclear region where an accretion disc forms, subsequently guiding the inflow of gas down to the black hole horizon. It is feared that gas at larger scales might still retain enough angular momentum and settle into a larger scale disc with very low or no inflow to form or replenish the inner accretion disc (on ~0.01 pc scales). In this paper we report on hydrodynamical simulations of rotating infalling gas shell…
Feeding the Dead: Neutral Gas Inflow in a Long-Quenched Ancient Massive Galaxy at $z\sim 2.7$ Observed with JWST/NIRSpec
Tufts University（塔夫茨大学）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；INAF - Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；Dipartimento di Fisica e Astronomia, Universitá di Bologna（博洛尼塔大学物理与天文学系）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）；European Space Research and Technology Centre（欧洲空间研究与技术中心）；Universitá degli studi di Milano-Bicocca（米兰比可卡大学）
Gaia has revealed clear evidence of bending waves in the vertical kinematics of stars in the Solar Neighbourhood. We study bending waves in two simulations, one warped, with the warp due to misaligned gas inflow, and the other unwarped. We find slow, retrograde bending waves in both models, with the ones in the warped model having larger amplitudes. We also find fast, prograde bending waves. Prograde bending waves in the unwarped model are very weak, in agreement with the expectation that these waves should decay on short, ~ crossing, timescales, due to strong winding. However, prograde bendin…
Recent studies have found higher galaxy metallicities in richer environments. It is not yet clear, however, whether metallicity-environment dependencies are merely an indirect consequence of environmentally dependent formation histories, or of environment related processes directly affecting metallicity. Here, we present a first detailed study of metallicity-environment correlations in a cosmological hydrodynamical simulation, in particular the Illustris simulation. Illustris galaxies display similar relations to those observed. Utilizing our knowledge of simulated formation histories, and lev…
Observations and semianalytical galaxy formation and evolution models (SAMs) have suggested the existence of a stellar mass-stellar metallicity relation (MZR), which is shown to be universal for different types of galaxies over a large range of stellar masses ($M_*\sim 10^3$-$10^{11}M_\odot$) and dark matter (DM) halo masses ($M_{\rm halo}\sim 10^9$-$10^{15}h^{-1}M_\odot$). In this work, we construct a chemical evolution model to investigate the origin of the MZR, including both the effects of gas inflows and outflows in galaxies. We solve the MZR from the chemical evolution model, by assuming…
We present a study of the gas cycle and star formation history in the central 500 pc of the Milky Way, known as Central Molecular Zone (CMZ). Through hydrodynamical simulations of the inner 4.5 kpc of our Galaxy, we follow the gas cycle in a completely self-consistent way, starting from gas radial inflow due to the Galactic bar, the channelling of this gas into a dense, star-forming ring/stream at ~ 200 - 300 pc from the Galactic centre, and the launching of galactic outflows powered by stellar feedback. We find that star formation activity in the CMZ goes through oscillatory burst/quench cycl…
We analyse the evolution of turbulence and gravitational instability of a galactic disc in a quasi-steady state governed by cosmological inflow. We focus on the possibility that the coupling between the in-streaming gas and the disc is maximal, e.g., via dense clumps, and ask whether the streams could be the driver of turbulence in an unstable disc with a Toomre parameter Q~1. Our fiducial model assumes an efficiency of ~0.5 per dynamical time for the decay of turbulence energy, and ~0.02 for each of the processes that deplete the disc gas, i.e., star formation, outflow, and inflow within the …
Deep HI observations of cold gas inflow and outflow
Netherlands Institute for Radio Astronomy (ASTRON)（荷兰射电天文研究所）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Centre for Astrophysics and Supercomputing, Swinburne University of Technology（斯威本科技大学天体物理与超算中心）；ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO3D)（ARC三维全天体物理卓越中心）；Graduate School of Science, Nagoya University（名古屋大学理学研究科）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；National Astronomical Observatory, Japan（日本国立天文台）；Department of Physics and Astronomy, Sejong University（世宗大学物理与天文学系）
A key uncertainty in galaxy evolution is the physics regulating star formation, ranging from small-scale processes related to the life-cycle of molecular clouds within galaxies to large-scale processes such as gas accretion onto galaxies. We study the imprint of such processes on the time-variability of star formation with an analytical approach tracking the gas mass of galaxies ("regulator model"). Specifically, we quantify the strength of the fluctuation in the star-formation rate (SFR) on different timescales, i.e. the power spectral density (PSD) of the star-formation history, and connect …
Quasars are high-luminosity active galactic nuclei believed to be powered by accretion of interstellar matter onto a super-massive black hole (SMBH) therein. Most of the observed energy is released in an accretion disk of inspiralling gas surrounding the SMBH. An enormous amount of fueling material is expected to be transported inwards. However, basic questions remain unanswered as to whether and how the accretion disks are supplied with external gas, since no disk-feeding inflow has hitherto been observed clearly. Here we report the discovery of highly redshifted broad absorption lines arisin…
We perform a stacking analysis of the neutral \nad\,$λλ$5889,5895\,Å ISM doublet using the SDSS DR7 spectroscopic data set to probe the prevalence and characteristics of cold (T\,$\lesssim$\,10$^{4}$\,K) galactic-scale gas flows in local (0.025$\leqslant z\leqslant$0.1) inactive and AGN-host galaxies across the SFR-M$_{*}$ plane. We find low-velocity outflows to be prevalent in regions of high SFRs and stellar masses (10 $\lesssim$log M$_{*}$/M$_{\odot}$ $\lesssim$ 11.5), however we do not find any detections in the low mass (log M$_{*}$/M$_{\odot}$ $\lesssim$ 10) regime. We also find tentativ…
Early studies of nearby Seyfert galaxies have led to the picture that the Narrow Line Region (NLR) is a cone-shaped region of gas ionized by radiation from a nuclear source collimated by a dusty torus, where the gas is in outflow. In this contribution, I discuss a 3D view of the NLR obtained via Integral Field Spectroscopy, showing that: (1) although the region of highest emission is elongated (and in some cases cone-shaped), there is also lower level emission beyond the "ionization cone", indicating that the AGN radiation leaks through the torus; (2) besides outflows, the gas kinematics inclu…
We study the gas distribution and kinematics of the inner kpc of six moderately luminous (43.43$\leq$log$L_{\rm bol}\leq$44.83) nearby ($0.004 \leq z \leq 0.014$) Seyfert galaxies observed with the Near-infrared Integral Field Spectrograph (NIFS) in the J(1.25$μ$m) and K(2.2$μ$m) bands. We analyse the most intense emission lines detected on these spectral wavebands: [Fe II] 1.2570 $μ$m and Pa$β$, which trace the ionised gas in the partially and fully ionised regions, and H$_2$2.1218$μ$m, that traces the hot ($\sim 2000$ K) molecular gas. The dominant kinematic component is rotation in the disc…
Evidence for gas accretion onto galaxies can be found throughout the universe. In this chapter, I summarize the direct and indirect signatures of this process and discuss the primary sources. The evidence for gas accretion includes the star formation rates and metallicities of galaxies, the evolution of the cold gas content of the universe with time, numerous indirect indicators for individual galaxies, and a few direct detections of inflow. The primary sources of gas accretion are the intergalactic medium, satellite gas and feedback material. There is support for each of these sources from ob…
Rapid, large amplitude variability at optical to X-ray wavelengths is now seen in an increasing number of Seyfert galaxies and luminous quasars. The variations imply a global change in accretion power, but are too rapid to be communicated by inflow through a standard thin accretion disc. Such discs are long known to have difficulty explaining the observed optical/UV emission from active galactic nuclei. Here we show that alternative models developed to explain these observations have larger scale heights and shorter inflow times. Accretion discs supported by magnetic pressure in particular are…
The spatial distributions of the most recently discovered ultra faint dwarf satellites around the Milky Way and the Andromeda galaxy are compared to the previously reported discs-of-satellites (DoS) of their host galaxies. In our investigation we pay special attention to the selection bias introduced due to the limited sky coverage of SDSS. We find that the new Milky Way satellite galaxies follow closely the DoS defined by the more luminous dwarfs, thereby further emphasizing the statistical significance of this feature in the Galactic halo. We also notice a deficit of satellite galaxies with …
Super-massive black holes (SMBHs) observed to have masses of $M_\bullet \sim 10^9 \, \mathrm{M_\odot}$ at $z\gtrsim6$, $<1$ Gyr after the Big Bang, are thought to have been seeded by massive black holes which formed before growing concurrently with the formation of their host galaxies. We model analytically the idealised growth of seed black holes, fed through gas inflow from growing proto-galaxy discs. The inflow depends on the disc gravitational stability and thus varies with black hole and disc mass. We find that for a typical host halo, the efficiency of angular momentum transport, as para…
We study the effect of surface brightness on the mass-metallicity relation using nearby galaxies whose gas content and metallicity profiles are available. Previous studies using fiber spectra indicated that lower surface brightness galaxies have systematically lower metallicity for their stellar mass, but the results were uncertain because of aperture effect. With stellar masses and surface brightnesses measured at WISE W1 and W2 bands, we re-investigate the surface brightness dependence with spatially-resolved metallicity profiles and find the similar result. We further demonstrate that the s…
We investigate the case for environmental quenching of the Fornax-mass satellite DDO 113, which lies only 9 kpc in projection from its host, the Large-Magellanic-Cloud-mass galaxy NGC 4214. DDO 113 was quenched about 1 Gyr ago and is virtually gas-free, while analogs in the field are predominantly star-forming and gas-rich. We use deep imaging obtained with the Large Binocular Telescope to show that DDO 113 exhibits no evidence of tidal disruption to a surface brightness of $μ_V\sim29$ mag $\text{arcsec}^{-2}$, based on both unresolved emission and resolved stars. Mass-analogs of DDO 113 in Il…
In this paper we explore a possible route of black hole seed formation that appeal to a model by Davies, Miller & Bellovary who considered the case of the dynamical collapse of a dense cluster of stellar black holes subjected to an inflow of gas. Here, we explore this case in a broad cosmological context. The working hypotheses are that (i) nuclear star clusters form at high redshifts in pre-galactic discs hosted in dark matter halos, providing a suitable environment for the formation of stellar black holes in their cores, (ii) major central inflows of gas occur onto these clusters due to inst…
We present new spectroscopic observations of Lyman-$α$ (Ly$α$) Blob 2 ($z \sim$ 3.1). We observed extended Ly$α$ emission in three distinct regions, where the highest Ly$α$ surface brightness (SB) center is far away from the known continuum sources. We searched through the MOSFIRE slits that cover the high Ly$α$ SB regions, but were unable to detect any significant nebular emission near the highest SB center. We further mapped the flux ratio of the blue peak to the red peak and found it is anti-correlated with Ly$α$ SB with a power-law index of $\sim$ -0.4. We used radiative transfer models wi…
The LEGARE Project. I. Chemical evolution model of the Nuclear Stellar Disc in a Bayesian framework
I.N.A.F. Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；IFPU, Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；Université Côte d’Azur, Observatoire de la Côte d’Azur（蔚蓝海岸大学蔚蓝海岸天文台）；CNRS（法国国家科学研究中心）；Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste（的里雅斯特大学物理系天文学部）；INFN Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；Division of Astrophysics, Department of Physics, Lund University（隆德大学物理系天体物理学部）
We study the effects of radial flows on Galactic chemical evolution. A simple analytic scheme is developed prescribing the coupling of infall from the intergalactic medium and radial flows within the disc based on angular momentum conservation. We show that model parameters are tightly constrained by the observed [Fe/H]-abundance gradient in the Galactic disc. By this comparison the average rotational velocity of the onfalling material can be constrained to 0.7 < v/V_c < 0.75, or respectively ~ 160 km/s when assuming a constant disc circular velocity of V_c = 220 km/s. We test the robustness o…
This chapter reviews how galactic inflows influence galaxy metallicity. The goal is to discuss predictions from theoretical models, but particular emphasis is placed on the insights that result from using models to interpret observations. Even as the classical G-dwarf problem endures in the latest round of observational confirmation, a rich and tantalizing new phenomenology of relationships between $M_*$, $Z$, SFR, and gas fraction is emerging both in observations and in theoretical models. A consensus interpretation is emerging in which star-forming galaxies do most of their growing in a quie…
Small dwarf companions have been long thought to have minimal influence on their host galaxy's evolution without undergoing direct impacts to the host's disc. However, in light of recent discoveries of coplanar, corotating satellite structures around the Milky Way, Andromeda, and Centaurus A, we use an N-body/test particle simulation to show that low-mass dwarf satellites within such structures are able to exert significant influence on their host's disc, driving spiral waves and inducing stellar scattering. This is accomplished through quasi-periodic alignments of multiple small satellites wi…
Composite Bulges -- V. Detecting signatures of gas inflows in IFU data: The MUSE view of ionised gas kinematics in nearby galaxies
Liverpool John Moores University（利物浦约翰摩尔大学）；University of Nottingham（诺丁汉大学）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理学研究所）；Universitäts-Sternwarte München（慕尼黑大学天文台）；Durham University（杜伦大学）；Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas（圣保罗大学天文学、地球物理与大气科学研究所）；University of Lancashire（兰开夏大学）；Universidad de La Laguna（拉帕鲁纳大学）
The impact of disc disruption on Milky Way satellite counts
Institute for Computational Cosmology, Durham University（达勒姆大学计算宇宙学研究所）；Department of Physics, Durham University（达勒姆大学物理系）；Lund Observatory, Division of Astrophysics, Department of Physics, Lund University（隆德大学天体物理学分部天文台）
