scholarly journals The ultra-diffuse galaxy NGC 1052-DF2 with MUSE

2019 ◽  
Vol 625 ◽  
pp. A77 ◽  
Author(s):  
Jérémy Fensch ◽  
Remco F. J. van der Burg ◽  
Tereza Jeřábková ◽  
Eric Emsellem ◽  
Anita Zanella ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Spectroscopic Analysis ◽  
Emission Lines ◽  
Spectral Fitting ◽  
Spatially Extended ◽  
The Subject ◽  
Stellar Body ◽  
Extended Emission ◽  
Intense Debate

NGC 1052-DF2, an ultra-diffuse galaxy (UDG), has been the subject of intense debate. Its alleged absence of dark matter, and the brightness and number excess of its globular clusters (GCs) at an initially assumed distance of 20 Mpc suggest a new formation channel for UDGs. We present the first systematic spectroscopic analysis of the stellar body and the GCs in this galaxy (six previously known and one newly confirmed member) using MUSE at the VLT. Even though NGC 1052-DF2 does not show any spatially extended emission lines, we report the discovery of three planetary nebulae (PNe). We conduct full spectral fitting on the UDG and the stacked spectra of all the GCs. The UDG’s stellar population is old, 8.9 ± 1.5 Gyr; metal poor, [M/H] = −1.07 ± 0.12; and with little or no α-enrichment. The stacked spectrum of all GCs indicates a similar age of 8.9 ± 1.8 Gyr, but a lower metallicity of [M/H] = −1.63 ± 0.09 and a similarly low α-enrichment. There is no evidence for a variation in age and metallicity in the GC population with the available spectra. The significantly more metal-rich stellar body with respect to its associated GCs, the age of the population, its metallicity, and its α-enrichment are all in line with other dwarf galaxies. NGC 1052-DF2 thus falls on the same empirical mass–metallicity relation as other dwarfs for the full distance range assumed in the literature. We find that both debated distance estimates (13 and 20 Mpc) are similarly likely, given the three discovered PNe.

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals Stellar parameters in the bulge cluster NGC 6553

1997 ◽  
Vol 189 ◽  
pp. 203-206 ◽  
Author(s):  
B. Barbuy ◽  
S. Ortolani ◽  
E. Bica ◽  
A. Renzini ◽  
M.D. Guarnieri
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Spectroscopic Analysis ◽  
Galactic Center ◽  
Stellar Populations ◽  
The Sun ◽  
Galactic Bulge ◽  
Complete Understanding ◽  
Luminosity Functions ◽  
Bulge Formation

Globular clusters in the Galactic bulge form a flattened system, extending from the Galactic center to about 4.5 kpc from the Sun (Barbuy et al. 1997). A study of abundance ratios in these clusters is very important for a more complete understanding of the bulge formation. In this work we present a spectroscopic analysis of individual stars in NGC 6553. This cluster is a key one because it is located at d⊙ ≍ 5.1 kpc, therefore relatively close to us, and at the same time it is representative of the Galactic bulge stellar population: (a) Ortolani et al. (1995) showed that NGC 6553 and NGC 6528 show very similar Colour-Magnitude Diagrams (CMDs), and NGC 6528 is located at d⊙ ≍ 7.83 kpc, very close to the Galactic center; (b) the stellar populations of the Baade Window is also very similar to that of NGC 6553 and NGC 6528 as Ortolani et al. (1995) have shown by comparing their luminosity functions.

An Extended Emission Line Region around Mrk 1172

2019 ◽  
Vol 15 (S359) ◽  
pp. 438-440
Author(s):  
Augusto Lassen ◽  
Rogério Riffel ◽  
Ana L. Chies-Santos ◽  
Evelyn Johnston ◽  
Boris Haeussler ◽  
...  
Keyword(s):  
Emission Line ◽  
Stellar Population ◽  
Emission Lines ◽  
Gas Content ◽  
Early Type ◽  
Strong Emission ◽  
Line Region ◽  
Hard Radiation ◽  
Star Formation Activity ◽  
Extended Emission

AbstractWe serendipitously found an intriguing Extended Emission Line Region (EELR) near the quiescent and massive early-type Mrk 1172, with a projected extension of approximately 14 × 14 kpc. Its irregular shape, high gas content, strong emission lines and proximity to an isolated possible faded quasar raise questions about the ionization of this gas and the nature of this object. Analyzing the stellar population in both objects we observe that the EELR has a dominance of young-intermediate and intermediate stellar populations (200 Myr < t < 1 Gyr) with significant star formation activity, while Mrk 1172 is dominated by old stellar population (t > 5 Gyr). BPT diagnostic diagrams indicate that the gas in the EELR is photoionized by hot massive stars rather than by a hard radiation field or by shocks. Further analysis on abundances of the gas and its kinematics shall be performed to better comprehend the nature of this object and how it is interacting with Mrk 1172.

scholarly journals How well can we determine ages and chemical abundances from spectral fitting of integrated light spectra?

2020 ◽  
Vol 499 (2) ◽  
pp. 2327-2339
Author(s):  
Geraldo Gonçalves ◽  
Paula Coelho ◽  
Ricardo Schiavon ◽  
Christopher Usher
Keyword(s):  
High Resolution ◽  
Wavelength Range ◽  
Globular Clusters ◽  
Stellar Population ◽  
High Resolution Spectroscopy ◽  
Chemical Abundances ◽  
Spectral Fitting ◽  
Light Spectra ◽  
The Ideal

ABSTRACT The pixel-to-pixel spectral fitting technique is often used in studies of stellar populations. It enables the user to infer several parameters from integrated light spectra such as ages and chemical abundances. In this paper, we examine the question of how the inferred parameters change with the choice of wavelength range used. We have employed two different libraries of integrated light spectra of globular clusters (GCs) from the literature and fitted them to stellar population models using the code Starlight. We performed tests using different regions of the spectra to infer reddening, ages, [Fe/H], and [α/Fe]. Comparing our results to age values obtained from isochrone fitting and chemical abundances from high-resolution spectroscopy, we find that: (1) the inferred parameters change with the wavelength range used; (2) the method in general retrieves good reddening estimates, specially when a wider wavelength range is fitted; (3) the ideal spectral regions for determination of age, [Fe/H], and [α/Fe] are 4170–5540, 5280–7020, and 4828–5364 Å, respectively; (4) the retrieved age values for old metal-poor objects can be several Gyr younger than those resulting from isochrone fitting. We conclude that, depending on the parameter of interest and the accuracy requirements, fitting the largest possible wavelength range may not necessarily be the best strategy.

scholarly journals Dust and star formation in the centre of NGC 3311

2020 ◽  
Vol 643 ◽  
pp. A119 ◽  
Author(s):  
T. Richtler ◽  
M. Hilker ◽  
M. Arnaboldi ◽  
C. E. Barbosa
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Globular Clusters ◽  
Stellar Population ◽  
Line Emission ◽  
Galaxy Cluster ◽  
Emission Lines ◽  
Strong Line ◽  
Rotating Disc ◽  
Neutral Gas

Context. NGC 3311 is the central galaxy of the Hydra I galaxy cluster. It has a hot interstellar medium and hosts a central dust lane with emission lines. These dust lanes are frequent in elliptical galaxies, but the case of NGC 3311 might be particularly interesting for problems of dust lifetime and the role of cool gas in the central parts. Aims. We aim to use archival HST images and MUSE data to investigate the central dust structure of NGC 3311. Methods. We used the tool PyParadise to model the stellar population and extract the emission lines. Results. The HST/ACS colour map reveals the known dust structures, but also blue spots, which are places of strong line emission. A dusty “mini-jet” emanates from the centre. The distribution of the emission line gas matches the dust silhouette almost exactly. Close to the brightest Hα emission, the ratio [NII]/Hα resembles that of HII-regions; in the outer parts, [NII] gets stronger and is similar to LINERLow-ionization nuclear emission-line region -like spectra. The gas kinematics is consistent with that of a rotating disc. The Doppler shifts of the strongest line emissions, which indicate the areas of highest star formation activity, smoothly fit into the disc symmetry. The metallicity is supersolar. The presence of neutral gas is indicated by the fit residuals of the stellar NaI D absorption line, which we interpret as interstellar absorption. We estimate the mass of the neutral gas to be of the order of the X-ray mass. The dynamical mass infers a stellar population of intermediate age, whose globular clusters have already been identified. Conclusions. Our findings can be harmonised in a scenario in which the star formation is triggered by the accretion of cold gas onto a pre-existing gas/dust disc or ring. Newly produced dust then contributes to the longevity of the dust.

scholarly journals Variables in Globular Clusters, the Common and the Rare

1973 ◽  
Vol 21 ◽  
pp. 3-7
Author(s):  
Helen Sawyer Hogg
Keyword(s):  
Globular Clusters ◽  
New Information ◽  
The Subject ◽  
The Common

The title of this talk is really just a different phrasing from one I have used at several IAU meetings on the subject of numbers and kinds of variables in globular clusters. To furnish this material, I have finished the Third Catalogue of Variables in Globular Clusters. Since many of you are coming to this Colloquium with new information, the Catalogue is in draft form with a request that corrections and additions be given me by October 2, after which the draft will go to the printer.The First Catalogue of Variables in Globular Clusters was published at this observatory in 1939 and the Second Catalogue in 1955. In 1966 appeared the excellent Catalogue of Variables South of Declination—29° by Fourcade, Laborde and Albarracin, with splendid large prints of identification charts.

scholarly journals Kinematics of Nuclei of Sc Galaxies

1980 ◽  
Vol 5 ◽  
pp. 191-191
Author(s):  
V. C. Rubin
Keyword(s):  
High Velocity ◽  
Stellar Population ◽  
Hii Regions ◽  
Emission Lines ◽  
High Luminosity ◽  
Rotation Curves ◽  
Velocity Gradients ◽  
Wide Range ◽  
Central Regions ◽  
Velocity Dispersions

For a sample of 21 Sc galaxies with a wide range of luminosities, of radii, and of masses, W. K. Ford and I have obtained spectra and determined rotation curves. By their kinematical behavior in their central regions, the Sc’s can be separated into two groups. Some galaxies, generally small and of low luminosity, have shallow central velocity gradients, reflecting their low central masses and densities. Other galaxies, most often large ones of high luminosity, have steep central velocity gradients. One reason this separation by central velocity gradients is of interest is because these galaxies exhibit other significant spectral differences which go hand-in-hand with the kinematical differences.The small, low luminosity galaxies show emission lines of Hα and [NII], with nuclear Ha sharp and stronger than [NII], and little or no stellar nuclear continuum, just as conventional HII regions. In contrast, the high luminosity galaxies show broad nuclear emission, with [NII] stronger than Ha. These galaxies have a strong red stellar continuum, arising from a red stellar population. The cause of the Hα[NII] intensity reversal in the nuclei of some galaxies remains unknown. However, the strong [NII] emission in generally high luminosity galaxies with massive nuclei, nuclei which show strong red continua, suggests that [Nil] intensity correlates with nuclear luminosity, and in turn with the density and velocity properties of the nuclear populations. We would expect high velocity dispersions and high bulge luminosities for galaxies with strong nuclear [NII] and steep central velocity gradients.

scholarly journals Female Assertion as an Antidote to Male Dominance: Mother Archetypes in Achebe’s Novels—Things Fall Apart, No Longer at Ease, and A Man of the People

2019 ◽  
Vol 1 (1) ◽  
pp. 13-19
Author(s):  
Jeremiah Mutuku Muneeni
Keyword(s):  
Women Characters ◽  
Male Dominance ◽  
Unit Of Analysis ◽  
Representation Of Women ◽  
Gender Balance ◽  
The People ◽  
Archetypal Criticism ◽  
The Subject ◽  
Things Fall Apart ◽  
Intense Debate

There has been an intense debate with regards to Chinua Achebe’s (mis)representation of women in his creative works, especially his first four novels. Some scholars have argued that Achebe is a patriarchal writer who has relegated women to the periphery. Nevertheless, a few have read subtle nuances of gender balance in his works. This paper is a continuation of this debate. Specifically, it argues that Achebe has created Mother Archetypes in his novels and if the same is not recognized, he will continue to be demonized as a gender insensitive writer. The unit of analysis is three of the five Achebe’s novels namely: Things Fall Apart, No Longer at Ease, and A Man of the People. The paper interrogates the aforementioned novels within the framework of archetypal criticism, with the aim of unearthing and examining Mother Archetypes inherent in them. The paper identifies religion, education, and justice as the spheres of life in which Achebe has created, empowered and elevated Mother Archetypes to be at par with their male counterparts. However, owing to the breadth of the subject, the paper dwells on education. The paper concludes that creation of empowered Mother Archetypes in Achebe’s novels is a symbolic relay in which women characters hand in the symbolic empowerment baton to the next woman in the next novel until the last one where the creation of a woman major character, Beatrice, wins the race against male dominance.

scholarly journals Die Abwesenheit der Phänomenologie in der deutschen Humangeographie

2017 ◽  
Vol 72 (3) ◽  
pp. 351-360 ◽  
Author(s):  
Jürgen Hasse
Keyword(s):  
Sense Perception ◽  
Material Body ◽  
Close Link ◽  
Basic Assumptions ◽  
Potential Gain ◽  
Spatially Extended ◽  
Critical Human Geography ◽  
Theoretical Conception ◽  
The Subject ◽  
Phenomenological View

Abstract. This article is written from the perspective of phenomenology. Its potential gain for a critical human geography is discussed in contrast to the paradigmatic frame of basic assumptions in constructivism. The example of atmospheres will illustrate another theoretical conception of space. In phenomenological view there happens not only a reality of things but also a circum-actuality is not spatially extended like a house or another material objective. Atmospheres are vital qualities (Dürckheim) we feel like a cloud in our sense perception in situations of awareness. This implies the necessity to make a difference between a material body (Körper) and a felt body (Leib). This epistemic knowledge will improve our critique of neoliberal societies, tuned by aestheticisation especially in glamour CBDs of postmodern cities. Finally there is a close link to the work of Michel Foucault, topped off in his The Hermeneutics of the Subject. References to the Critical Theory (Frankfurter Schule) are connected.

scholarly journals Formación de educadores sociales en Cataluña: reflexiones acerca de los grados de Educación Social ofrecidos por dos universidades de Barcelona (p. 45-64)

2017 ◽  
Author(s):  
Marina Minussi Franco
Keyword(s):  
Professional Training ◽  
Educational Institutions ◽  
Social Education ◽  
Academic Context ◽  
Autonomous Region ◽  
The Social ◽  
Education Careers ◽  
The Subject ◽  
The University ◽  
Intense Debate

Este artigo trata de descrever os processos de formação profissional de educa-dores sociais no âmbito da educação universitária na Comunidade Autônomada Catalunha, na Espanha. Nos últimos anos, devido ao surgimento de novasformas de exclusão social, ao aumento das desigualdades e à crescente globali-zação, verifica-se um aprofundamento do debate sobre a profissão do educadorsocial, suas competências e funções e, ao mesmo tempo, sobre a necessidade derepensar sua formação. Este trabalho faz parte de um projeto mais amplo sobreo assunto e apresenta uma revisão bibliográfica baseada no contexto acadêmicoespanhol, com uma descrição das propostas formativas dos cursos de graduaçãode Educação Social de duas universidades catalãs de importante reconhecimentointernacional: Universidade de Barcelona e Universidade Autônoma de Barce-lona. Os resultados evidenciam a necessidade de uma maior aproximação entreo processo formativo que os educadores recebem no âmbito universitário e asnecessidades reais presentes nas instituições socioeducativas.Palavras-chave: Educação social. Educador social. Formação profissional.Competências.ResumenEste artículo trata de describir dos procesos de formación profesional de educa-dores sociales en el ámbito de la educación universitaria en la Comunidad Autó-noma de Cataluña, España. En los últimos años, a consecuencia del surgimientode nuevas formas de exclusión social, del aumento de las desigualdades y de lacreciente globalización, se verifica una intensificación del debate sobre la profe-sión del educador social, sus competencias, sus funciones y a la vez sobre la ne-cesidad de repensar su formación. Este trabajo forma parte de un proyecto másamplio acerca del tema y presenta una revisión bibliográfica basada en el contex-to académico español, al lado de una descripción de las propuestas formativas delas carreras de Educación Social de dos universidades catalanas de importante re-conocimiento internacional: Universidad de Barcelona y Universidad Autónomade Barcelona. Los resultados evidencian la importancia de la aproximación entreel proceso formativo que los educadores reciben en el ámbito universitario y lasnecesidades reales presentes en las instituciones socioeducativas.Palabras clave: Educación social. Educador social. Formación profesional.Competencias.AbstractThis article looks at the courses offered at two higher-education institutions fortraining social educators in the autonomous region of Catalonia, Spain. In recentyears, due to new forms of social exclusion, the escalation of inequality andincreasing globalization, there is a more intense debate on the profession of thesocial educator, their competences, roles and, at the same time, on the need torethink their training. This work is part of a larger project on the subject and pre-sents a bibliographical review based on the Spanish academic context, along witha description of the training proposals of the Social Education careers withintwo Catalan universities: University of Barcelona and Autonomous University ofBarcelona. The results show the importance of combining the training processoffered to social educators in the university context with the real needs of thesocio-educational institutions where they will practice their profession.Keywords: Social education. Social educator. Professional training. Competencies.

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