Evolution of disk galaxies in MOdified Gravity (MOG)

2019 ◽  
Vol 14 (S353) ◽  
pp. 152-153
Author(s):  
Neda Ghafourian ◽  
Mahmood Roshan
Keyword(s):  
Modified Gravity ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Free Parameters

AbstractEvolution and the formation of bars in the galactic disks is studied in the context of Modified Gravity (MOG) by using N-body simulations. It is found that changing the value of free parameters of the model can effectively alter the strength of the bar and disk’s stability.

scholarly journals Warps and Accretion

2010 ◽  
Vol 6 (S277) ◽  
pp. 71-74 ◽  
Author(s):  
Gyula I. G. Józsa
Keyword(s):  
Star Formation ◽  
Intergalactic Medium ◽  
Ambient Medium ◽  
Basic Feature ◽  
Optical Disk ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Star Forming ◽  
Show Evidence ◽  
Excitation Mechanisms

AbstractWarps are a basic feature of disk galaxies. Usually they occur at radii where the optical disk fades and become most pronounced in the outermost gaseous disks.As such, warps present a massive reservoir to replenish star forming material in the inner, star forming disks. Furthermore, some possible excitation mechanisms for warps connect their formation to the accretion of extragalctic material. Interactions or mergers with gas-rich companions or the direct accretion of the ambient intergalactic medium might lead to the formation of warps, at the same time supplementing fuel to maintain star formation in galactic disks.Employing a number of H i studies of warped galaxies, including ultra-deep observations of the prototype warped galaxies NGC 5907 and NGC 4013, I discuss whether the observed kinematics may show evidence for a connection of warps and accretion from the ambient medium.

scholarly journals The influence of star clusters on galactic disks: new insights in star-formation in galaxies

2008 ◽  
Vol 4 (S254) ◽  
pp. 209-220
Author(s):  
Pavel Kroupa
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Disk Galaxies ◽  
Galactic Disks

AbstractStars form in embedded star clusters which play a key role in determining the properties of a galaxy's stellar population. A large fraction of newly born massive stars are shot out from dynamically unstable embedded-cluster cores spreading them to large distances before they explode. Embedded clusters blow out their gas once the feedback energy from the new stellar population overcomes its binding energy, leading to cluster expansion and in many cases dissolution into the galaxy. Galactic disks may be thickened by such processes, and some thick disks may be the result of an early epoch of vigorous star-formation. Binary stellar systems are disrupted in clusters leading to a lower fraction of binaries in the field, while long-lived clusters harden degenerate-stellar binaries such that the SNIa rate may increase by orders of magnitude in those galaxies that were able to form long-lived clusters. The stellar initial mass function of the whole galaxy must be computed by adding the IMFs in the individual clusters. The resulting integrated galactic initial mass function (IGIMF) is top-light for SFRs < 10 M⊙/yr, and its slope and, more importantly, its upper stellar mass limit depend on the star-formation rate (SFR), explaining naturally the mass–metallicity relation of galaxies. Based on the IGIMF theory, the re-calibrated Hα-luminosity–SFR relation implies dwarf irregular galaxies to have the same gas-depletion time-scale as major disk galaxies, implying a major change of our concept of dwarf-galaxy evolution. A galaxy transforms about 0.3 per cent of its neutral gas mass every 10 Myr into stars. The IGIMF-theory also naturally leads to the observed radial Hα cutoff in disk galaxies without a radial star-formation cutoff. It emerges that the thorough understanding of the physics and distribution of star clusters may be leading to a major paradigm shift in our understanding of galaxy evolution.

scholarly journals Toward a new understanding of disk galaxy formation

2019 ◽  
Vol 15 (S352) ◽  
pp. 347-347
Author(s):  
Susan Kassin
Keyword(s):  
Early Universe ◽  
Galaxy Formation ◽  
Disk Galaxy ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Analytic Models ◽  
The Universe ◽  
Open Issues

AbstractOne of the most important open issues in astronomy is the assembly of galactic disks. Over the last decade this has been addressed with large surveys of the internal kinematics of galaxies spanning the last 10 billion years of the universe. I will discuss recent results from the field that show the kinematic assembly of disk galaxies since a redshift of 2.5, including recent deep 10–30 hour observations by my group with the DEIMOS spectrograph on Keck. These results strongly challenge traditional analytic models of galaxy formation and provide an important benchmark for simulations. Furthermore, I will discuss our plans for extending measurements to higher redshifts with future instruments such as the JWST's NIRSpec IFU and the E-ELT's MOSAIC and HARMONI IFUs. From mock JWST and E-ELT observations of simulated galaxies, we are learning that interpreting these observations of galaxies in the early universe, when merging is frequent, is not necessarily straightforward.

scholarly journals Quantifying the Redistribution of Mass in Galactic Disks due to Bars

2010 ◽  
Vol 6 (S277) ◽  
pp. 242-245
Author(s):  
Patricia Sánchez-Blázquez ◽  
Isabel Pérez ◽  
Pierre Ocvirk
Keyword(s):  
Evolutionary Process ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Chemical Abundance ◽  
Star Forming ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Bulge Region ◽  
Disc Region ◽  
Inside Out

AbstractNumerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric components and vice-versa. The most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate because the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary process. We present here a pilot study of the gas and stellar metallicity and age distributions in a sample of barred and non-barred galaxies using 2D spectroscopic observations. We found that the majority of the stellar mass in our sample is composed of old (~10 Gyr) stars. This is true in the bulge and the disc region, even beyond two disc scalelengths. In the disc region, a larger fraction of young stars is present in the external parts of the disc compared with the inner disc. The disc growth is, therefore, compatible with a moderate inside-out formation scenario, where the luminosity-weighted age changes from ~10 Gyrs in the centre, to ~4 Gyrs at two disc scalelengths, depending upon the galaxy. However, the presence of substructure, like star forming rings, can produce stellar population trends that are not directly related with the growing of the disc but to the bar potential. In the disc region, the metallicity gradient always decrease with the radius. In the bulge region this is not always true and we find inverse metallicity gradients in several galaxies.

scholarly journals Barred Galaxies: Intrinsic or Extrinsic?

1996 ◽  
Vol 157 ◽  
pp. 339-348 ◽  
Author(s):  
M. Noguchi
Keyword(s):  
Simple Model ◽  
Gravitational Instability ◽  
Dynamical Property ◽  
Disk Galaxies ◽  
Early Type ◽  
Late Type ◽  
Galactic Disks ◽  
Barred Galaxies ◽  
Tidal Interactions ◽  
Key Parameter

AbstractA unified picture is presented for the formation of bars in galaxies of different morphological types based on a simple model of the growth of galactic disks by gas infall from haloes. The infall timescale is found to be a key parameter which determines the dynamical property of the resulting disk. It is suggested that the bars in early-type disk galaxies have been formed in tidal interactions with other galaxies whereas those in late-type galaxies formed spontaneously due to gravitational instability (bar instability) in their disks.

scholarly journals Simulations on the Collisional Properties of Gas in Galaxies

2004 ◽  
Vol 217 ◽  
pp. 228-229
Author(s):  
Yves Revaz ◽  
Daniel Pfenniger
Keyword(s):  
Disk Galaxies ◽  
Simple Method ◽  
Free Parameters ◽  
Slow Cycling ◽  
Cold Gas

In this work, we explore a simple method with few free parameters, which describes the global dynamical consequences on disk galaxies of a slow cycling of gas between the interstellar, almost collisionless very cold gas and the warm collisional phases, with a secular transformation of a fraction of warm gas into stars.

scholarly journals A first attempt to differentiate between modified gravity and modified inertia with galaxy rotation curves

2020 ◽  
Vol 636 ◽  
pp. A56 ◽  
Author(s):  
Jonas Petersen ◽  
Federico Lelli
Keyword(s):  
Modified Gravity ◽  
Surface Brightness ◽  
Analytical Models ◽  
Disk Galaxies ◽  
Rotation Curves ◽  
Quality Requirements ◽  
Modified Newtonian Dynamics ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

The phenomenology of modified Newtonian dynamics (MOND) on galaxy scales may point to more fundamental theories of either modified gravity (MG) or modified inertia (MI). In this paper, we test the applicability of the global deep-MOND parameter Q which is predicted to vary at the 10% level between MG and MI theories. Using mock-observed analytical models of disk galaxies, we investigate several observational uncertainties, establish a set of quality requirements for actual galaxies, and derive systematic corrections in the determination of Q. Implementing our quality requirements to the SPARC database yields 15 galaxies, which are close enough to the deep-MOND regime as well as having rotation curves that are sufficiently extended and sampled. For these galaxies, the average and median values of Q seem to favor MG theories, albeit both MG and MI predictions are in agreement with the data within 1.5σ. Improved precision in the determination of Q can be obtained by measuring extended and finely-sampled rotation curves for a significant sample of extremely low-surface-brightness galaxies.

scholarly journals The Challenge of Modelling Galactic Disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 437-444
Author(s):  
Andreas Burkert
Keyword(s):  
Predictive Power ◽  
Initial Conditions ◽  
Galactic Disk ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Disk Formation ◽  
Secular Evolution ◽  
Formation And Evolution ◽  
Microphysical Processes ◽  
Multi Phase

AbstractDetailed models of galactic disk formation and evolution require knowledge about the initial conditions under which disk galaxies form, the boundary conditions that affect their secular evolution and the microphysical processes that drive the multi-phase interstellar medium and regulate star formation. Unfortunately, up to now, most of these ingredients are still poorly understood. The challenge therefore is to still construct realistic models of galactic disks with predictive power.

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