scholarly journals Dark matter and H i in ultra-diffuse galaxy UGC 2162

2019 ◽  
Vol 488 (3) ◽  
pp. 3222-3230 ◽  
Author(s):  
Chandreyee Sengupta ◽  
T C Scott ◽  
Aeree Chung ◽  
O Ivy Wong
Keyword(s):  
Dark Matter ◽  
Radio Telescope ◽  
Galaxy Formation ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Rotational Velocity ◽  
Rotation Velocity ◽  
The Galaxy

ABSTRACT Our GMRT (Giant Metrewave Radio Telescope) H i observations of the ultra-diffuse galaxy (UDG) UGC 2162, projected ∼ 300 kpc from the centre of the M 77 group, reveal it to a have an extended H i disc ($R_{\rm H\,{\small I}}/R_{25}$ ∼ 3.3) with a moderate rotational velocity (Vrot ∼ 31 km s−1). This Vrotis in line with that of dwarf galaxies with similar H i mass. We estimate an Mdyn of ∼1.14 × 109 M⊙ within the galaxy’s $R_ \rm {H\,{\small I}}$ ∼ 5.2 kpc. Additionally, our estimates of M200 for the galaxy from NFW models are in the range of 5.0–8.8 × 1010 M⊙. Comparing UGC 2162 to samples of UDGs with H i detections show it to have amongst the smallest Re with its MH i/M* being distinctly higher and g – icolour slightly bluer than typical values in those samples. We also compared H i and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to determine the origin of the galaxy’s present-day optical form from our study, its normal H i rotation velocity in relation to its H i mass, H i morphology, environment, and dwarf mass DM halo ruled out some of the proposed ultra-diffuse galaxy formation scenarios for this galaxy.

scholarly journals NIHAO – XXV. Convergence in the cusp-core transformation of cold dark matter haloes at high star formation thresholds

2020 ◽  
Vol 499 (2) ◽  
pp. 2648-2661
Author(s):  
Aaron A Dutton ◽  
Tobias Buck ◽  
Andrea V Macciò ◽  
Keri L Dixon ◽  
Marvin Blank ◽  
...  
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Good Description ◽  
Good Match ◽  
Virial Mass ◽  
Density Threshold

ABSTRACT We use cosmological hydrodynamical galaxy formation simulations from the NIHAO project to investigate the response of cold dark matter (CDM) haloes to baryonic processes. Previous work has shown that the halo response is primarily a function of the ratio between galaxy stellar mass and total virial mass, and the density threshold above which gas is eligible to form stars, n[cm−3]. At low n all simulations in the literature agree that dwarf galaxy haloes are cuspy, but at high n ≳ 100 there is no consensus. We trace halo contraction in dwarf galaxies with n ≳ 100 reported in some previous simulations to insufficient spatial resolution. Provided the adopted star formation threshold is appropriate for the resolution of the simulation, we show that the halo response is remarkably stable for n ≳ 5, up to the highest star formation threshold that we test, n = 500. This free parameter can be calibrated using the observed clustering of young stars. Simulations with low thresholds n ≤ 1 predict clustering that is too weak, while simulations with high star formation thresholds n ≳ 5, are consistent with the observed clustering. Finally, we test the CDM predictions against the circular velocities of nearby dwarf galaxies. Low thresholds predict velocities that are too high, while simulations with n ∼ 10 provide a good match to the observations. We thus conclude that the CDM model provides a good description of the structure of galaxies on kpc scales provided the effects of baryons are properly captured.

scholarly journals The Large Range of Dark Matter content in Dwarf Galaxies and its Implications

1996 ◽  
Vol 171 ◽  
pp. 435-435
Author(s):  
S.A. Pustilnik ◽  
V.A. Lipovetsky ◽  
J.-M. Martin ◽  
T.X. Thuan
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Range ◽  
Dwarf Galaxy ◽  
Rotational Velocity ◽  
Matter Content ◽  
Optical Observations ◽  
Strong Interactions ◽  
Formation Mechanisms ◽  
Mass Ratio

We present the analysis of a new set of radio and optical observations of a large sample of Byurakan Blue Compact Galaxies. HI spectra were obtained with the Nançay 300-m and Green Bank 43-m radio telescopes. CCD-images were taken with the KPNO 0.9-m and Whipple Observatory 1.2-m telescopes. Dark Matter (DM) to luminous mass ratios in these BCGs were found to vary from about less than 0.5 up to 14. Recent data taken from the literature indicate this same range. This result has important consequences on models of dwarf galaxy formation, indicating possibly different formation mechanisms. The standard CDM model of dwarfs formation requires large DM halos. However the formation of dwarfs as tidal debris resulting from strong interactions of massive spirals leads naturally to dwarfs with low content of DM. On Fig.1 we show DM to luminous mass ratio versus rotational velocity for our BCGs and some other galaxies.

scholarly journals The edge of the Galaxy

2020 ◽  
Vol 496 (3) ◽  
pp. 3929-3942 ◽  
Author(s):  
Alis J Deason ◽  
Azadeh Fattahi ◽  
Carlos S Frenk ◽  
Robert J J Grand ◽  
Kyle A Oman ◽  
...  
Keyword(s):  
Dark Matter ◽  
Radial Velocity ◽  
Milky Way ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Space Distribution ◽  
Radial Density ◽  
The Galaxy ◽  
Galaxy Population

ABSTRACT We use cosmological simulations of isolated Milky Way (MW)-mass galaxies, as well as Local Group (LG) analogues, to define the ‘edge’ – a caustic manifested in a drop in density or radial velocity – of Galactic-sized haloes, both in dark matter and in stars. In the dark matter, we typically identify two caustics: the outermost caustic located at ∼1.4r200m, corresponding to the ‘splashback’ radius, and a second caustic located at ∼0.6r200m, which likely corresponds to the edge of the virialized material that has completed at least two pericentric passages. The splashback radius is ill defined in LG-type environments where the haloes of the two galaxies overlap. However, the second caustic is less affected by the presence of a companion, and is a more useful definition for the boundary of the MW halo. Curiously, the stellar distribution also has a clearly defined caustic, which, in most cases, coincides with the second caustic of the dark matter. This can be identified in both radial density and radial velocity profiles, and should be measurable in future observational programmes. Finally, we show that the second caustic can also be identified in the phase–space distribution of dwarf galaxies in the LG. Using the current dwarf galaxy population, we predict the edge of the MW halo to be 292 ± 61 kpc.

The Future of Dwarf Galaxy Research: What Simulations will Predict?

2018 ◽  
Vol 14 (S344) ◽  
pp. 17-26
Author(s):  
Laura V. Sales
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Matter Content ◽  
Dark Matter Halos ◽  
Matter Distribution ◽  
The Future ◽  
Dark Matter Distribution

AbstractWe present a summary of the predictions from numerical simulations to our understanding of dwarf galaxies. It centers the discussion around the Λ Cold Dark Matter scenario (ΛCDM) but discusses also implications for alternative dark matter models. Four key predictions are identified: the abundance of dwarf galaxies, their dark matter content, their relation with environment and the existence of dwarf satellites orbiting dwarf field galaxies. We discuss tensions with observations and identify the most exciting predictions expected from simulations in the future, including i) the existence of “dark galaxies” (dark matter halos without stars), ii) the ability to resolve the structure (size, morphology, dark matter distribution) in dwarfs and iii) the number of ultra-faint satellites around dwarf galaxies. All of these predictions shall inform future observations, not only the faintest galaxies to be discovered within the Local Volume but also distant dwarfs driving galaxy formation in the early universe.

scholarly journals Associations of dwarf galaxies in a ΛCDM Universe

2020 ◽  
Vol 499 (4) ◽  
pp. 5932-5940
Author(s):  
C Yamila Yaryura ◽  
Mario G Abadi ◽  
Stefan Gottlöber ◽  
Noam I Libeskind ◽  
Sofía A Cora ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Velocity Dispersion ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Local Volume ◽  
Λcdm Model ◽  
First Time ◽  
Maximum Threshold

ABSTRACT Associations of dwarf galaxies are loose systems composed exclusively of dwarf galaxies. These systems were identified in the Local Volume for the first time more than 30 yr ago. We study these systems in the cosmological framework of the Λ cold dark matter (ΛCDM) model. We consider the Small MultiDark Planck simulation and populate its dark matter haloes by applying the semi-analytic model of galaxy formation SAG. We identify galaxy systems using a friends-of-friends algorithm with a linking length equal to $b=0.4 \, {\rm Mpc}\, h^{-1}$ to reproduce the size of dwarf galaxy associations detected in the Local Volume. Our samples of dwarf systems are built up removing those systems that have one or more galaxies with stellar mass larger than a maximum threshold Mmax. We analyse three different samples defined by ${\rm log}_{10}(M_{\rm max}[{\rm M}_{\odot }\, h^{-1}]) = 8.5, 9.0$, and 9.5. On average, our systems have typical sizes of $\sim 0.2\, {\rm Mpc}\, h^{-1}$, velocity dispersion of $\sim 30 {\rm km\, s^{-1}}$, and estimated total mass of $\sim 10^{11} {\rm M}_{\odot }\, h^{-1}$. Such large typical sizes suggest that individual members of a given dwarf association reside in different dark matter haloes and are generally not substructures of any other halo. Indeed, in more than 90 per cent of our dwarf systems their individual members inhabit different dark matter haloes, while only in the remaining 10 per cent members do reside in the same halo. Our results indicate that the ΛCDM model can naturally reproduce the existence and properties of dwarf galaxies’ associations without much difficulty.

scholarly journals The Structure of the Stellar Hosts in Blue Compact Dwarf Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 300-300
Author(s):  
R.O. Amorín ◽  
J.A.L. Aguerri ◽  
L.M. Cairós ◽  
N. Caon ◽  
C. Muñoz-Tuñón
Keyword(s):  
Galaxy Formation ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Structural Parameters ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Galaxy Formation And Evolution ◽  
Radial Profiles ◽  
Low Surface Brightness ◽  
Formation And Evolution

AbstractBlue compact dwarf (BCD) galaxies are gas-rich, low-luminosity (Mb≳-18 mag) and compact systems, currently undergoing violent star-formation burst (Sargent & Searle 1970). While it was initially hypothesized that they were very young galaxies (e.g. Sargent & Searle 1970, et al. 1988), the subsecuent detection of an extended, redder stellar host galaxy showed that the vast majority of them are old systems (e.g. Gil de Paz et al. 2003,2005). BCDs play an important role for understanding the process of galaxy formation and evolution.The structural properties of the low surface brightness stellar host in BCDs are often studied by fitting r1/n models to the outer regions of their radial profiles. The limitations imposed by the presence of a large starburst emission overlapping the underlying component makes this kind of analysis a difficult task.We propose a two-dimensional fitting methodology in order to improve the extraction of the structural parameters of the LSB host Amorín et al. 2006, submitted). A set of ideal simulations are presented in order to test the reliability of the method and to determine its robustness and flexibility. We present the different steps of the method discussing its advantages and weaknesses. We compare the results for a sample of eight objects with those already obtained using a one-dimensional technique (Caon et al. 2005).We fit a PSF convolved Sérsic model to the BVR images with the GALFIT publicly software (Peng et al. 2002). We restrict the fit to the stellar host by masking out the starburst region and take special care to minimize the sky-subtraction uncertainties. Consistency checks are performed to assess the reliability and accuracy of the derived structural parameters.We obtain robust fits for all the sample galaxies, all of which, except one, show low Sérsic indices n—very close to 1—with good agreement in the three bands. These findings suggest that the stellar hosts in BCDs have near-exponential profiles. Since the Sérsic index n of host galaxies is important in the context of the possible structural and evolutionary connections among the different types of dwarf galaxies, we are currently extending the study to a larger sample of objects. This kind of studies will help us to understand the mechanisms that form and shape BCD galaxies, and how they relate to the other dwarf galaxy classes.

scholarly journals The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

2021 ◽  
Vol 650 ◽  
pp. A113
Author(s):  
Margot M. Brouwer ◽  
Kyle A. Oman ◽  
Edwin A. Valentijn ◽  
Maciej Bilicki ◽  
Catherine Heymans ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Weak Lensing ◽  
Mass Relation ◽  
Gravitational Acceleration ◽  
Radial Acceleration ◽  
The Galaxy ◽  
The Difference

We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.

scholarly journals Galaxy Formation and Large-Scale Structures in a Two-Component Dark Matter Scenario

1988 ◽  
Vol 130 ◽  
pp. 427-428
Author(s):  
Masayuki Umemura
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Large Scale Structures ◽  
Two Component ◽  
Scale Structures

A universe dominated by both hot (HDM) and cold dark matter (CDM) is proposed. In this context, the new features for the formation of dwarf galaxies, Lyα clouds, galaxies, and large-scale structures are presented.

scholarly journals Refracting into ultra-diffuse galaxy NGC 1052-DF2 by passing near the centre of NGC 1052

2020 ◽  
Vol 495 (1) ◽  
pp. L144-L148 ◽  
Author(s):  
Ran Huo
Keyword(s):  
Dark Matter ◽  
Physical Mechanism ◽  
Dwarf Galaxy ◽  
Recent Observation ◽  
Tidal Effect ◽  
Natural Consequence ◽  
Formation Theory ◽  
The Galaxy ◽  
Standard Structure ◽  
Flat Distribution

ABSTRACT The recent observation of the ultra-diffuse galaxy NGC 1052-DF2 shows a galaxy may lack dark matter, which becomes a challenge to the standard structure formation theory. Here, we show that such phenomena can be a natural consequence if the NGC 1052-DF2 had experienced a single passage within a few kpc to the centre of the galaxy NGC 1052. The tidal effect of NGC 1052 in the encounter will heat the NGC 1052-DF2, and stretch the previous dwarf galaxy significantly into its current size. The relative lack of dark matter in the observed region is a natural consequence of the dark matter limited total amount in the corresponding small central region before the encounter, together with a systematic underestimation of the trace mass estimator method during revirialization after the encounter. The observed flat distribution of the ultra-diffuse galaxy can be reproduced with a cored initial star profile, which is a major improvement compared with the previous work. Our results show no need for introducing any new physical mechanism, as well as an alternative origin of an ultra-diffuse galaxy without repeated pericentre passage.

Sign in / Sign up

Export Citation Format

Share Document