On the Formation of Galaxy Halos: Comparing NGC 5128 and the Local Group Members

2001 ◽  
Vol 122 (6) ◽  
pp. 3065-3069 ◽  
Author(s):  
William E. Harris ◽  
Gretchen L. H. Harris
Keyword(s):  
Local Group ◽  
Galaxy Halos ◽  
Group Members

Methanol Masers in the Andromeda Galaxy

2017 ◽  
Vol 13 (S336) ◽  
pp. 113-116
Author(s):  
Ylva M. Pihlström ◽  
Loránt O. Sjouwerman
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
Local Group ◽  
Angular Resolution ◽  
Transverse Velocity ◽  
High Angular Resolution ◽  
Dynamic Force ◽  
Group Members ◽  
Methanol Masers ◽  
Motion Studies

AbstractIs M31 going to collide with the Milky Way, or spiral around it? Determining the gravitational potential in the Local Group has been a challenge since it requires 3D space velocities and orbits of the members, and most objects have only had line-of-sight velocities measured. Compared to the less massive group members, the transverse velocity of M31 is of great interest, as after the Milky Way, M31 is the most dominant constituent and dynamic force in the Local Group. Proper motion studies of M31 are preferentially done using masers, as continuum sources are much weaker, and are enabled through the high angular resolution provided by VLBI in the radio regime. The challenges of achieving high astrometric accuracy at high VLBI frequencies (> 20 GHz) makes observations at lower frequencies attractive, as long as sufficient angular resolution is obtained. In particular, we have discovered 6.7 GHz methanol masers in M31 using the VLA, and here we will address their feasibility as VLBI proper motion targets using a set of global VLBI observations.

scholarly journals Globular clusters in M31, Local Group, and external galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 120-127 ◽  
Author(s):  
Søren S. Larsen
Keyword(s):  
Chemical Composition ◽  
Globular Clusters ◽  
Local Group ◽  
Full Extent ◽  
Light Spectra ◽  
Galaxy Halos ◽  
External Galaxies ◽  
Nearby Galaxies

AbstractThroughout most of the Local Group, globular clusters (GCs) remain recognisable as extended objects in ground-based images taken in good seeing conditions. However, studying the full extent of the GC systems is challenging because of the large sky area that needs to be surveyed and recent years have seen dramatic progress in our knowledge of GC populations in nearby galaxies, thanks to large imaging surveys. At the same time, techniques for deriving detailed abundances from integrated-light spectra of GCs are maturing so that detailed comparisons of the chemical composition for GCs in different galaxies can now be made. Such comparisons may shed important light on the properties of proto-galactic fragments that were accreted onto galaxy halos. Nevertheless, our census of Local Group GCs probably remains far from complete, in particular at low luminosities and for very extended clusters.

scholarly journals Stellar Content of Local Group Galaxies - An Introduction

1999 ◽  
Vol 192 ◽  
pp. 3-16 ◽  
Author(s):  
Sidney van den Bergh
Keyword(s):  
Milky Way ◽  
Local Group ◽  
Large Fraction ◽  
Polar Group ◽  
Stellar Content ◽  
Groups Of Galaxies ◽  
Ic 10 ◽  
Sky Survey ◽  
Group Members ◽  
Ngc 6822

In The Realm of the Nebulae, Hubble (1936) first drew attention to the fact that the Milky Way system and the Andromeda galaxy belong to a small cluster that also contains M32, M33, the Magellanic Clouds, NGC 205, NGC 6822 and IC 1613. Hubble also listed IC 10 as a possible member of what he referred to as “the Local Group”. Inspection of the prints of the Palomar Sky Survey shows (van den Bergh 1962) that a large fraction of all field galaxies are located in such small groups or clusters. Our Milky Way system therefore appears to be situated in a rather typical region of space. All of the well-established Local Group members that are listed above are at distances D ≤ 1.0 Mpc. A conservative limit D < 1.5 Mpc may therefore be used to search for new Local Group members. An additional criterion for physical membership in the Local Group is that a candidate member with solar apex distance θ and radial velocity Vr should lie close to the Vr versus cos θ relation for well-established Local Group members (Courteau & van den Bergh 1999). Finally candidates may be disqualified from membership if they appear projected on nearby groups of galaxies that are centered at distances greater than 1.5 Mpc. In particular the Local Group candidates NGC 1560, NGC 1569, UGC-A86 and Cassiopeia 1 were excluded because they appear projected on (or near) the IC 342/Maffei group. Furthermore NGC 55 and UKS 2323-326 were excluded because they appear projected on (or near) the Sculptor (= South Polar) group. Observational data on 35 probable Local Group members are given in Table 1.

scholarly journals A turbulence study in Dwarf Irregular galaxies

2006 ◽  
Vol 2 (S237) ◽  
pp. 484-484
Author(s):  
Margarita Valdez-Gutiérrez ◽  
Ivânio Puerari
Keyword(s):  
Fourier Transform ◽  
Local Group ◽  
Power Spectra ◽  
Spectra Analysis ◽  
Preliminary Results ◽  
Irregular Galaxies ◽  
Group Members ◽  
Ism Structure ◽  
Dwarf Irregular Galaxies

AbstractWe present preliminary results of a Fourier transform power spectra analysis carried out on a sample of dwarf irregular galaxies and Local Group members. This project is intended to study turbulence and the ISM structure in irregulars as a class.

scholarly journals The Nature of the Local Group

2004 ◽  
Vol 193 ◽  
pp. 19-30
Author(s):  
Antonio Aparicio
Keyword(s):  
Galaxy Formation ◽  
Local Group ◽  
Short Review ◽  
Star Formation History ◽  
Significant Information ◽  
Milky Way Galaxy ◽  
Galaxy Formation And Evolution ◽  
Group Members ◽  
Formation And Evolution ◽  
Tidal Streams

AbstractThe Local Group provides an interesting and representative sample of galaxies in the rest of the Universe. The high accuracy with which many problems can be addressed in Local Group galaxies is of paramount importance for understanding galaxy formation and evolution. This contribution presents a short review of overall Local Group properties followed by short discussions of five topics in which the study of Local Group members provides particularly significant information. These topics are only examples of the usefulness and potential of Local Group research. The five selected topics are the formation of the Milky Way, galaxy destruction and tidal streams, detailed galactic chemical evolution, star formation history determination, and low surface brightness extended structures.

scholarly journals Resolving the stellar outskirts of six Milky Way-like galaxies beyond the Local Group

2016 ◽  
Vol 11 (S321) ◽  
pp. 43-43
Author(s):  
A. Monachesi ◽  
E. F. Bell ◽  
D. J. Radburn-Smith ◽  
B. Harmsen ◽  
R. S. de Jong ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Local Group ◽  
Spiral Galaxies ◽  
Disk Galaxies ◽  
Galaxy Halos ◽  
Model Predictions ◽  
The Galaxy ◽  
Thick Disks ◽  
Stellar Properties

AbstractModels of galaxy formation in a hierarchical universe predict substantial scatter in the halo-to-halo stellar properties, owing to stochasticity in galaxies’ merger histories. Currently, only few detailed observations of galaxy’s halos are available, mainly for the Milky Way and M31. The Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey is the largest study to date of the resolved stellar populations in the outskirts of disk galaxies and its observations offer a direct test of model predictions. Here we present the results we obtain for six highly inclined nearby Milky Way-mass spiral galaxies. We find a great diversity in the properties of their stellar halos.

scholarly journals The New Local Group Galaxy Candidates Cas dSph, Peg dSph = And VI, and Cam A

1999 ◽  
Vol 192 ◽  
pp. 284-287 ◽  
Author(s):  
C. Gallart ◽  
D. Martínez-Delgado ◽  
A. Aparicio ◽  
W. L. Freedman
Keyword(s):  
Local Group ◽  
Star Forming ◽  
Andromeda Galaxy ◽  
Group Members ◽  
Group Galaxy ◽  
Local Group Galaxy

We present observations of the new Local Group galaxy candidates Cassiopeia dSph, Pegasus dSph = And VI and Camelopadalis A. Our deep color-magnitude diagrams show that the first two galaxies are certainly Local Group members, and likely dSph galaxies at a distance similar to that of the Andromeda galaxy. Cam A seems to be a star-forming galaxy situated considerably further away.

scholarly journals When Can Every Group Member be Above the Group's Average? The Weighted LOGE Theory of Social Comparison Biases

2020 ◽  
Author(s):  
Shir Etgar
Keyword(s):  
Local Group ◽  
Comparative Judgment ◽  
The Other ◽  
Individual Member ◽  
Sequential Method ◽  
Positive Group ◽  
Group Members ◽  
Individual Group Member ◽  
Group Member ◽  
General Standard

The Non Selective Superiority bias (NSSB) is defined as the tendency to judge each randomly chosen group member from a positive group as better than the other group members from the same group. While this is a reliable and robust bias, its origins are still debated. Internal explanations of the bias posit that NSSB is caused by some distortion in the internal comparisons between the focal group member and the other members of the same group. According to unique attribute theory (Chambers, 2010), NSSB occurs because each individual group member of a positive group is judged according to the dimension that positively distinguishes this individual member from the other members of the same positive group. According to focalism theories (e.g., Moore &amp; Kim, 2003; Posavacet al., 2004), judges focus excessively on the standing of the focal member on the judged quality rather than the corresponding status of the others in the group on the same quality (i.e., "this candidate is highly curious" rather than "this candidate is curious more than other candidates in the short list").Giladi and Klar (2002) proposed an external explanation for the bias, meaning, suggested that the bias occurs due to a distortion that is not related to a comparison between the focal group members. Their approach, LOGE (Local comparisons- General Standards), suggested that in addition to the internal comparison between the judged group member and the others in the local group, a second, simultaneous comparison also takes place. This is a comparison between each judged group member and the general standard, which represents the judge's knowledge and experience about the range of qualities within the larger category that pertains to the judged local group. This external standard is logically irrelevant to the comparison process; however, cognitively, it cannot be avoided. According to LOGE, NSSB is due to the intrusive effect of the external comparison with the general stand pertaining to the judged quality. The original LOGE theory paid no special attention to the relative judgmental weights of the two components (i.e., internal and external; DIFFL and DIFFG) in the resulting comparative judgment. Therefore, it was impossible to draw experimental predictions from the original theory. This dissertation attempts to rectify this issue. This work proposed a better specified version of LOGE which is termed Weighted-LOGE (W-LOGE). In this version, the relative weights of DIFFL and DIFFG can vary. This enables me to test the main LOGE prediction: the greater the judgmental focus is ascribed to DIFFG (rather than to DIFFL), the greater the comparative bias should be. This prediction suggests that when the focus is on the internal commonalities (rather than differences) within the local group, judges are likely to be less preoccupied with within-group comparisons (i.e., DIFFL) and consequently, will be engaged to a greater extent in the external comparison (i.e., DIFFG). W-LOGE will predict that in this case, a greater NSSB will occur. In the first empirical section, we compared this prediction to unique attribute theory's predictions, Across three studies, we found support to the W-LOGE predictions, suggesting that NSSB increasing when group members are similar to each other. The next empirical section compared between W-LOGE and Focalism. This section employed a sequential comparative judgment method, in which each group member was judged in turn against the others in the group. Focalism approaches argued that the origin of NSSB is the neglect of the non-focal group members during the comparative judgment. Therefore, when the focal member role alternates in each comparative judgment from one group member to another, Focalism assume that NSSB should progressively diminish or even totally disappear. Here as well, across three studies, evidence supported W-LOGE theory.In the final experimental section of this work, the sequential method used to directly contrast W-LOGE with both Focalism and unique attribute approaches. If judges repeatedly consider how superior each local group member is compared to the general standard, as seen at the previous section, what will happen when they additionally focus on within-group similarities? W-LOGE predicts that when the focus is on within-group similarities, the pluses of each of the local group members versus the general standards might even bolster the judgments and thus NSSB could even gradually increase with successive judgments. Across three additional study, this prediction was supported. Across these nine studies, which utilized the W-LOGE model, I found support to the experimental predictions draw from the LOGE theory. These studies corroborate the claim that the logically irrelevant comparison of judged group members with an irrelevant general standard is the main cause of NSSB, since the relative judgmental weight assigned to this external comparison regulates the magnitude of the bias.

scholarly journals Resolving the stellar halos of six massive disk galaxies beyond the Local Group

2015 ◽  
Vol 11 (S317) ◽  
pp. 222-227 ◽  
Author(s):  
Antonela Monachesi ◽  
Eric F. Bell ◽  
David J. Radburn-Smith ◽  
Roelof S. de Jong ◽  
Jeremy Bailin ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Local Group ◽  
Density Profiles ◽  
Galaxy Halos ◽  
The Galaxy ◽  
Stellar Halo ◽  
Red Giant ◽  
Stellar Properties ◽  
Giant Branch Stars

AbstractModels of galaxy formation in a hierarchical universe predict substantial scatter in the halo-to-halo stellar properties, owing to stochasticity in galaxies' merger histories. Currently, only few detailed observations of stellar halos are available, mainly for the Milky Way and M31. We present the stellar halo color/metallicity and density profiles of red giant branch stars out to ~60 kpc along the minor axis of six massive nearby Milky Way-like galaxies beyond the Local Group from the Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey. This enlargement of the sample of galaxies with observations of stellar halo properties is needed to understand the range of possible halo properties, i.e. not only the mean properties but also the halo-to-halo scatter, what a ‘typical’ halo looks like, and how similar the Milky Way halo is to other halos beyond the Local Group.

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

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