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Formação estelar no complexo de nuvens moleculares em Monoceros; Star Formation in the Molecular Cloud Complex in Monoceros

Gama, Diana Renata Gonçalves
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/05/2012 PT
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66.05%
Comparamos duas nuvens moleculares, Rosette (RMC) e Monoceros R2 (Mon R2), localizadas no Complexo de Monoceros com o objetivo de estudar suas condições físicas relacionadas às primeiras fases da formação estelar. Tratam-se de regiões interessantes por apresentarem características que podem ser confrontadas com a hipótese de formação estelar provocada pela passagem de nuvens de altas velocidades atravessando o plano Galáctico (HVCs). Avaliamos as propriedades dessas nuvens por meio de mapas de vários traçadores da formação estelar com base em diferentes bandas espectrais visando estudar a estrutura de densidade das nuvens, bem como os objetos estelares jovens, em particular as fontes masers de H2O que apresentam características típicas de protoestrelas massivas. Nossa análise permitiu verificar algumas semelhanças entre RMC e Mon R2, mas também nos revelou diferenças interessantes. De uma forma geral há concordância entre AV, CO e emissão de poeira em 100 microns; RMC possui muitos clumps, entretanto poucos aglomerados e nebulosidades exceto uma única região HII principal (NGC2244) enquanto Mon R2 apresenta poucos clumps, vários aglomerados jovens e pequenas nebulosidades; em RMC há mais estrelas massivas...

Formação estelar induzida por choques de Supernovas e por Turbulência Magneto-hidrodinâmica ; Star formation triggered by Supernovae shocks and magneto-hydrodynamical turbulence

Leão, Márcia Regina Moreira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/11/2012 PT
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66.21%
Neste trabalho investigamos os efeitos de choques (induzidos por supernovas) e de turbulência magneto-hidrodinâmica no processo de formação estelar. Primeiramente, considerando o impacto de um remanescente de supernova (RSN) com uma nuvem neutra magnetizada derivamos analiticamente um conjunto de condições através das quais estas interações podem levar à formação de estruturas densas capazes de tornarem-se gravitacionalmente instáveis e formar estrelas. Usando estas condições, construímos diagramas do raio do RSN, $R_$, versus a densidade inicial da nuvem, $n_c$, os quais delimitam um domínio no espaço paramétrico onde a formação estelar é permitida. Estes diagramas foram testados através de simulações numéricas magneto-hidrodinâmicas tridimensionais (3D MHD) onde seguimos a evolução espaço-temporal da interação de um RSN com uma nuvem auto-gravitante. Verificamos que a análise numérica está de acordo com os resultados previstos pelos diagramas. Observamos ainda que a presença de um campo magnético fraco, $\sim 1 \; \mu$G, inicialmente homogêneo e perpendicular à velocidade de impacto do RSN, resulta em uma pequena diminuição da região permitida para formação estelar nos diagramas quando comparado a diagramas para nuvens não magnetizadas. Já um campo magnético mais intenso ($\sim 10\;\mu$G) causa um encolhimento significativo nestas...

Near infrared study of the S140 star formation region

Benjou, Jessica ; Pipher, Judith Lynn (1940 - )
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:14 leaves
ENG
Relevância na Pesquisa
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Thesis (B.S.)--University of Rochester. Dept. of Physics and Astronomy, 2003.; Young stellar clusters hold a wealth of previously untapped information. They have in the past been obscured to examinations due to the observational wavelengths that were available. By exploring these regions in the infrared, we will be able to observationally resolve more details of the star formation process and cluster anatomy. These findings will facilitate the development of more accurate star formation theory and explanation of causal interactions among young stellar cluster components such as ionized HI! regions, molecular clouds, and OB associations. I am studying the 5140 cluster through the SIRTF Young Cluster Project at the University of Rochester. My region of study is a cometary globule on the edge of the Cepheus bubble. A BO V star, HD21880 ionizes the region. It appears to be creating the bow shaped HII region that may be shock exciting star formation in the conjoining molecular cloud, L1204. Three clear infrared sources in the 5140 core verify that star formation is active. One of these has a detected outflow (Park & Minh 1995). Regions such as these are especially useful for detecting embedded protostars and brown dwarves. Study of disk formation is only possible before these young objects reach the main sequence because the disk dissipates as the star evolves. Brown dwarfs normally are two dim for detection. As young...

A Near infrared study of the star formation region L988E

Barczys, Matthew ; Pipher, Judith Lynn (1940 - )
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:32 leaves
ENG
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Thesis (B.S.)--University of Rochester. Dept. of Physics and Astronomy, 1999.; We present new near infrared images of the star formation region, L988e, that help to establish this region as a relatively young cluster of new and forming (pre-main sequence) intermediate mass stars. These images span a significant portion of the near infrared region: broadband images at J (1.25 um), H (1.65 um), and K (2.23 um), in addition to spectral line imaging of Hz at 2.122 urn, [Fell] (singly-ionized forbidden iron transition) at 2.166 um, and polycyclic aromatic hydrocarbons at 3.29 and 3.40 um. The derived properties are used to ascertain some of the current properties of the star formation region and its constituents, and to present a general understanding of the region that unifies and expands upon what others have observed.

Modeling the effects of star formation histories on H$alpha$ and ultraviolet fluxes in nearby dwarf galaxies

Weisz, D.R.; Johnson, B.D.; Johnson, L.C.; Skillman, E.D.; Lee, J.C.; Kennicutt, R.C.; Calzetti, D.; Van Zee, L.; Bothwell, M.S.; Dalcanton, J.J.; Dale, D.A.; Williams, B.F.
Fonte: The American Astronomical Society Publicador: The American Astronomical Society
Tipo: Artigo de Revista Científica
EN_US
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We consider the effects of non-constant star formation histories (SFHs) on $ ext{H}alpha$ and GALEX far-ultraviolet (FUV) star formation rate (SFR) indicators. Under the assumption of a fully populated Chabrier initial mass function (IMF), we compare the distribution of $ ext{H}alpha$-to-FUV flux ratios from ~1500 simple, periodic model SFHs with observations of 185 galaxies from the $ extit{Spitzer}$ Local Volume Legacy survey. We find a set of SFH models that are well matched to the data, such that more massive galaxies are best characterized by nearly constant SFHs, while low-mass systems experience burst amplitudes of ~30 (i.e., an increase in the SFR by a factor of 30 over the SFR during the inter-burst period), burst durations of tens of Myr, and periods of ~250 Myr; these SFHs are broadly consistent with the increased stochastic star formation expected in systems with lower SFRs. We analyze the predicted temporal evolution of galaxy stellar mass, R-band surface brightness, $ ext{H}alpha$-derived SFR, and blue luminosity, and find that they provide a reasonable match to observed flux distributions. We find that our model SFHs are generally able to reproduce both the observed systematic decline and increased scatter in $ ext{H}alpha$-to-FUV ratios toward low-mass systems...

Evolution of star-forming dwarf galaxies: characterizing the star formation scenarios

Martín Manjón, M.L.; Mollá, M.; Díaz, Angeles I.; Terlevich, R.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
ENG
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This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Martín-Manjón, M.L., Mollá, M., Díaz, A.I. and R. Terlevich. Evolution of star-forming dwarf galaxies: characterizing the star formation scenarios. Monthly Notices of the Royal Astronomical Society 420 (2012): 1294-1308

The roles of star formation and AGN activity of IRS sources in the HerMES fields

Feltre, A.; Hatziminaoglou, Evanthia; Hernán Caballero, Antonio; Fritz, J.; Franceschini, Alberto; Bock, Jamie; Cooray, Asantha R.; Farrah, Duncan; González Solares, Eduardo A.; Ibar, Edo; Isaak, K. G.; Lo Faro, B.; Marchetti, L.; Oliver, Seb; Page, M.;
Fonte: Oxford University Press; Royal Astronomical Society Publicador: Oxford University Press; Royal Astronomical Society
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
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In this work, we explore the impact of the presence of an active galactic nucleus (AGN) on the mid- and far-infrared (IR) properties of galaxies as well as the effects of simultaneous AGN and starburst activity in the same galaxies. To do this, we apply a multicomponent, multiband spectral synthesis technique to a sample of 250 μm selected galaxies of the Herschel Multi-tiered Extragalactic Survey (HerMES), with Infrared Spectrograph (IRS) spectra available for all galaxies. Our results confirm that the inclusion of the IRS spectra plays a crucial role in the spectral analysis of galaxies with an AGN component improving the selection of the best-fitting hot dust (torus) model. We find a correlation between the obscured star formation rate, SFRIR, derived from the IR luminosity of the starburst component, and SFRPAH, derived from the luminosity of the PAH features, LPAH, with SFRFIR taking higher values than SFRPAH. The correlation is different for AGN- and starburst-dominated objects. The ratio of LPAH to that of the starburst component, LPAH/LSB, is almost constant for AGN-dominated objects but decreases with increasing LSB for starburst-dominated objects. SFRFIR increases with the accretion luminosity, Lacc, with the increase less prominent for the very brightest...

Properties of bulgeless disk galaxies: II star formation as a function of circular velocity

Watson, Linda C.; Martini, Paul; Lisenfeld, Ute; Wong, Man-Hong; B??ker, Torsten; Schinnerer, Eva
Fonte: American Astronomical Society; Institute of Physics (IOP) Publicador: American Astronomical Society; Institute of Physics (IOP)
Tipo: Pré-impressão
ENG
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We study the relation between the surface density of gas and star formation rate in 20 moderately inclined, bulgeless disk galaxies (Sd-Sdm Hubble types) using CO(1-0) data from the IRAM 30 m telescope, H I emission line data from the VLA/EVLA, H?? data from the MDM Observatory, and polycyclic aromatic hydrocarbon emission data derived from Spitzer IRAC observations. We specifically investigate the efficiency of star formation as a function of circular velocity (v circ). Previous work found that the vertical dust structure and disk stability of edge-on, bulgeless disk galaxies transition from diffuse dust lanes with large scale heights and gravitationally stable disks at v circ < 120 km s???1 (M * lsim 1010 M ???) to narrow dust lanes with small scale heights and gravitationally unstable disks at v circ > 120 km s???1. We find no transition in star formation efficiency ($Sigma _{ m SFR}/Sigma _{ m H,mathsc{i}+{ m H}_{2}}$) at v circ = 120 km s???1 or at any other circular velocity probed by our sample (v circ = 46-190 km s???1). Contrary to previous work, we find no transition in disk stability at any circular velocity in our sample. Assuming our sample has the same dust structure transition as the edge-on sample, our results demonstrate that scale height differences in the cold interstellar medium of bulgeless disk galaxies do not significantly affect the molecular fraction or star formation efficiency. This may indicate that star formation is primarily affected by physical processes that act on smaller scales than the dust scale height...

Collisional debris as laboratories to study star formation

Boquien, M??r??dic; Duc, P.-A.; Wu, Y.; Charmandaris, V.; Lisenfeld, Ute; Braine, J.; Brinks, E.; Iglesias-P??ramo, J.; Xu, C. K.
Fonte: American Astronomical Society; Institute of Physics (IOP) Publicador: American Astronomical Society; Institute of Physics (IOP)
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
66.16%
In this paper we address the question whether star formation is driven by local processes or the large scale environment. To do so, we investigate star formation in collisional debris where the gravitational potential well and velocity gradients are shallower and compare our results with previous work on star formation in non-interacting spiral and dwarf galaxies. We have performed multiwavelength spectroscopic and imaging observations (from the far-ultraviolet to the mid-infrared) of 6 interacting systems, identifying a total of 60 star-forming regions in their collision debris. Our analysis indicates that in these regions a) the emission of the dust is at the expected level for their luminosity and metallicity, b) the usual tracers of star formation rate display the typical trend and scatter found in classical star forming regions, and c) the extinction and metallicity are not the main parameters governing the scatter in the properties of intergalactic star forming regions; age effects and variations in the number of stellar populations, seem to play an important role. Our work suggests that local properties such as column density and dust content, rather than the large scale environment seem to drive star formation. This means that intergalactic star forming regions can be used as a reliable tool to study star formation.

Polychromatic view of intergalactic star formation in NGC 5291

Boquien, M??r??dic; Duc, P.-A.; Braine, J.; Brinks, E.; Lisenfeld, Ute; Charmandaris, V.
Fonte: European Southern Observatory (ESO); Springer Verlag Publicador: European Southern Observatory (ESO); Springer Verlag
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
66.1%
Context.Star formation (SF) takes place in unusual places such as way out in the intergalactic medium out of material expelled from parent galaxies.; Aims.Whether SF proceeds in this specific environment in a similar way than in galactic disks is the question we wish to answer. Particularly, we address the reliability of ultraviolet, H$alpha$ and mid-infrared as tracers of SF in the intergalactic medium.; Methods.We have carried out a multiwavelength analysis of the interacting system NGC 5291 , which is remarkable for its extended HI ring hosting numerous intergalactic HII regions. We combined new ultraviolet (GALEX) observations with archival H$alpha$, 8 $mu$m (Spitzer Space Telescope) and HI (VLA B-array) images of the system.; Results.We have found that the morphology of the star forming regions, as traced by the ultraviolet, H$alpha$, and 8 $mu$m emission is similar. The 8.0 $mu$m infrared emission, normalised to emission from dust at 4.5 $mu$m, which is known to be dominated by PAH bands, is comparable to the integrated emission of dwarf galaxies of the same metallicity and to the emission of individual HII regions in spirals. The 8.0 $mu$m in the intergalactic environment is therefore an estimator of the star formation rate which is as reliable in that extreme environment as it is for spirals. There is a clear excess of ultraviolet emission compared to individual HII regions in spirals...

Intergalactic star formation

Duc, P.-A.; Boquien, M??r??dic; Braine, J.; Brinks, E.; Lisenfeld, Ute; Charmandaris, V.
Fonte: Universidade de Granada Publicador: Universidade de Granada
Tipo: Conferência ou Objeto de Conferência
ENG
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66.05%
Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength study presented here. We collected VLA/HI, UV/GALEX, optical Halpha and MIR/Spitzer images of a few nearby interacting systems chosen for their prominent "intergalactic" star formation activity. Preliminary results on the spectacular collisional HI ring around NGC 5291 are presented.

Gas flows and star formation as a consequence of galaxy interaction in compact groups

Vogt, Frédéric Paul André
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD)
EN
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The environment of galaxies is known to influence their evolution via a wide range of processes, such as tidal interactions, ram-pressure stripping, or galaxy harassment. However, the exact interconnectivity between the large scale environment-driven mechanisms and the other internal processes (starburst, star formation quenching, nuclear activity, and both outflows and inflows) remains poorly understood. This thesis describes the use of the WiFeS and MUSE integral field spectrographs to study gas flows and star formation activity inside two members of compact groups of galaxies: HCG 16c and HCG 91c. In particular, WiFeS and MUSE are used to resolve scales of 1 kpc at the distances of HCG 16c and HCG 91c - the size of giant molecular clouds and HII regions - in an effort to tie the environment to its impact within the disks of the galaxies. HCG 16c is found to host an asymmetric, bipolar, rotating galactic wind, powered by a nuclear starburst. Emission line ratio diagnostics indicate that photoionization is the dominant excitation mechanism at the base of the wind. The asymmetry of the wind is likely caused by one of the two lobes of the wind-blown bubble bursting out of its HI envelope. The characteristics of the wind suggest that it is caught early (a few Myr) in the wind evolution sequence. The wind is also quite different to the galactic wind in the partner galaxy HCG 16d which contains a symmetric...

Star Formation in Collision Debris: Insights from the modeling of their Spectral Energy Distribution

Boquien, M??r??dic; Duc, P.-A.; Galliano, F.; Braine, J.; Lisenfeld, Ute; Charmandaris, V.; Appleton, P. N.
Fonte: American Astronomical Society; Institute of Physics (IOP) Publicador: American Astronomical Society; Institute of Physics (IOP)
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
66.11%
During galaxy-galaxy interactions, massive gas clouds can be injected into the intergalactic medium which in turn become gravitationally bound, collapse and form stars, star clusters or even dwarf galaxies. The objects resulting from this process are both "pristine", as they are forming their first generation of stars, and chemically evolved because the metallicity inherited from their parent galaxies is high. Such characteristics make them particularly interesting laboratories to study star formation. After having investigated their star-forming properties, we use photospheric, nebular and dust modeling to analyze here their spectral energy distribution (SED) from the far-ultraviolet to the mid-infrared regime for a sample of 7 star-forming regions. Our analysis confirms that the intergalactic star forming regions in Stephan's Quintet, around Arp 105, and NGC 5291, appear devoid of stellar populations older than 10^9 years. We also find an excess of light in the near-infrared regime (from 2 to 4.5 microns) which cannot be attributed to stellar photospheric or nebular contributions. This excess is correlated with the star formation rate intensity suggesting that it is probably due to emission by very small grains fluctuating in temperature as well as the polycyclic aromatic hydrocarbons (PAH) line at 3.3 micron. Comparing the attenuation via the Balmer decrement to the mid-infrared emission allows us to check the reliability of the attenuation estimate. It suggests the presence of embedded star forming regions in NGC 5291 and NGC 7252. Overall the SED of star-forming regions in collision debris (and Tidal Dwarf Galaxies) resemble more that of dusty star-forming regions in galactic disks than to that of typical star-forming dwarf galaxies.

A turnover in the galaxy main sequence of star formation at M*∼ 10¹⁰ M☉ for redshifts z< 1.3

Lee, Nicholas; Sanders, D. B.; Casey, Caitlin M.; Toft, Sune; Scoville, N. Z.; Hung, Chao-Ling; Le Floc'h, Emeric; Ilbert, Olivier; Zahid, H. Jabran; Aussel, Hervé; Capak, Peter; Kartaltepe, Jeyhan S.; Kewley, Lisa J.; Li, Yanxia; Schawinski, Kevin; Shet
Fonte: IOP Publishing Publicador: IOP Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.03%
The relationship between galaxy star formation rates (SFRs) and stellar masses (M∗) is reexamined using a mass-selected sample of ∼62,000 star-forming galaxies at z 1.3 in the COSMOS 2 deg²field. Using new far-infrared photometry from Herschel-PACS and SPIRE and Spitzer-MIPS 24μm, along with derived infrared luminosities from the NRK method based on galaxies’ locations in the restframe color–color diagram (NUV − r) versus (r − K), we are able to more accurately determine total SFRs for our complete sample. At all redshifts, the relationship between median SFR and M∗ follows a power law at low stellar masses, and flattens to nearly constant SFR at high stellar masses. We describe a new parameterization that provides the best fit to the main sequence and characterizes the low mass power-law slope, turnover mass, and overall scaling. The turnover in the main sequence occurs at a characteristic mass of about M0 ∼ 10¹⁰ Mʘ at all redshifts. The low mass power-law slope ranges from 0.9–1.3 and the overall scaling rises in SFR as a function of (1 +z)⁴˙¹²±⁰˙¹⁰. A broken power-law fit below and above the turnover mass gives relationships of SFR ∝ M⁰˙⁸⁸±⁰˙⁰⁶ ∗ below the turnover mass and SFR ∝ M⁰˙²⁷±⁰˙⁰⁴ ∗ above the turnover mass. Galaxies more massive than M∗ 1010 M have a much lower average specific star formation rate (sSFR) than would be expected by simply extrapolating the traditional linear fit to the main sequence found for less massive galaxies.

Star formation in ultra-faint dwarfs: continuous or single-aged bursts?

Webster, David; Bland-Hawthorn, Joss; Sutherland, Ralph
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Artigo de Revista Científica Formato: 6 pages
Relevância na Pesquisa
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We model the chemical evolution of six ultra-faint dwarfs (UFDs): Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I based on their recently determined star formation histories. We show that two single-age bursts cannot explain the observed [α/Fe] versus [Fe/H] distribution in these galaxies and that some selfenrichment is required within the first burst. An alternative scenario is modeled, in which star formation is continuous except for short interruptions when one or more supernovae temporarily blow the dense gas out from the center of the system. This model allows for self-enrichment and can reproduce the chemical abundances of the UFDs in which the second burst is only a trace population. We conclude that the most likely star formation history is one or two extended periods of star formation, with the first burst lasting for at least 100 Myr. As found in earlier work, the observed properties of UFDs can be explained by formation at a low mass (Mvir ~ 107 Me), rather than being stripped remnants of much larger systems.; D.W. is funded by an Australian Postgraduate Award. J.B.H. is funded by an ARC Laureate Fellowship.

Star formation activity and gas stripping in the Cluster Projected Phase-Space (CPPS)

Fernández, Jonathan David Hernández; Haines, C. P.; Diaferio, A.; Iglesias-Paramo, J.; Oliveira, Claudia Lucia Mendes de; Vilchez, J. M.
Fonte: Oxford University Press; Oxford Publicador: Oxford University Press; Oxford
Tipo: Artigo de Revista Científica
ENG
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This work is focused on the study of the distribution in the Cluster Projected Phase-Space (CPPS) of passive(ly-evolving) and star-forming galaxy populations and also, the intense and quiescent star-forming populations for a set of nine nearby z < 0.05 galaxy clusters. Furthermore, we compare the CPPS distribution of the passive galaxy population with the accreted halo population of a set of 28 simulated clusters and the star-forming population with the non-accreted population. We consider various cluster accretion epochs and accretion radii, where it is assumed that star formation in galaxies becomes quenched, in order to segregate the accreted population from the non-accreted population. Just applying this segregation in simulations, we get a qualitative agreement between the CPPS distributions of the passive and the accreted populations and also between the star-forming and the non-accreted populations. The uncertainty in cluster centring strongly affects the pronounced cuspy profiles of the projected density and also, it can explain the main difference (i.e. inner slope) between the CPPS distribution of passive and accreted populations. The CPPS density of star-forming galaxies and the intensity of ram-pressure stripping present an opposite trend throughout the CPPS. This implies that ram-pressure stripping significantly contributes to modulate the observed CPPS distribution of star-forming galaxies in cluster virial regions and their surroundings. The significant fraction of star-forming galaxies at the projected centre of clusters are mainly those galaxies with low line-of-sight velocities and they can be mainly identified as those galaxies with a remaining star formation activity (quiescent star-forming galaxies) inside the physical virial region or...

The star formation efficiency in Stephan's Quintet intragroup regions

Natale, G.; Tuffs, Richard J.; Xu, C. K.; Popescu, Cristina C.; Fischera, J.; Lisenfeld, Ute; Lu, N.; Appleton, P. N.; Dopita, M.; Duc, P.-A.; Gao, Y.; Reach, W.; Sulentic, J.; Yun, M. S.
Fonte: Astronomical Society of the Pacific Publicador: Astronomical Society of the Pacific
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
66.11%
Conference proceedings "Galaxy Mergers in an evolving Universe", 23-28 October 2011, Hualien, Taiwan.; We investigated the star formation efficiency for all the dust emitting sources in Stephan's Quintet (SQ). We inferred star formation rates using Spitzer MIR/FIR and GALEX FUV data and combined them with gas column density measurements by various authors, in order to position each source in a Kennicutt-Schmidt diagram. Our results show that the bright IGM star formation regions in SQ present star formation efficiencies consistent with those observed within local galaxies. On the other hand, star formation in the intergalactic shock region seems to be rather inhibited.

Dust emission and star formation in Stephan's Quintet

Natale, G.; Tuffs, Richard J.; Xu, C. K.; Popescu, Cristina C.; Fischera, J.; Lisenfeld, Ute; Lu, N.; Appleton, P. N.; Dopita, M.; Duc, P.-A.; Gao, Y.; Reach, W.; Sulentic, J.; Yun, M. S.
Fonte: American Astronomical Society; Institute of Physics (IOP) Publicador: American Astronomical Society; Institute of Physics (IOP)
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
66.08%
We analyse a comprehensive set of MIR/FIR observations of Stephan's Quintet (SQ), taken with the Spitzer Space Observatory. Our study reveals the presence of a luminous (L_{IR}\approx 4.6x10^43 erg/s) and extended component of infrared dust emission, not connected with the main bodies of the galaxies, but roughly coincident with the X-ray halo of the group. We fitted the inferred dust emission spectral energy distribution of this extended source and the other main infrared emission components of SQ, including the intergalactic shock, to elucidate the mechanisms powering the dust and PAH emission, taking into account collisional heating by the plasma and heating through UV and optical photons. Combining the inferred direct and dust-processed UV emission to estimate the star formation rate (SFR) for each source we obtain a total SFR for SQ of 7.5 M(sun)/yr, similar to that expected for non-interacting galaxies with stellar mass comparable to the SQ galaxies. Although star formation in SQ is mainly occurring at, or external to the periphery of the galaxies, the relation of SFR per unit physical area to gas column density for the brightest sources is similar to that seen for star-formation regions in galactic disks. We also show that available sources of dust in the group halo can provide enough dust to produce up to L_{IR}\approx 10^42 erg/s powered by collisional heating. Though a minority of the total infrared emission (which we infer to trace distributed star-formation)...

Formación estelar en cuásares; Star formation in quasars

Jara Martínez, Enrique
Fonte: Universidade de Cantabria Publicador: Universidade de Cantabria
Tipo: Dissertação de Mestrado
SPA
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66.05%
RESUMEN: Se han obtenido los flujos a distintas longitudes de onda de una muestra de 43 cuásares no oscurecidos. A partir de la información recogida se han construido las distribuciones espectrales de energía de estos objetos astronómicos, lo que ha permitido obtener las luminosidades correspondientes al infrarrojo lejano y las luminosidades de los núcleos galácticos activos (UV-infrarrojo cercano). De esta manera ha sido posible cuantificar la contribución de la formación estelar y del núcleo galáctico activo a la luminosidad en el infrarrojo lejano. Hemos podido comprobar, de manera cualitativa la existencia de una relación entre la luminosidad del núcleo activo y la luminosidad en el infrarrojo lejano. Se ha encontrado que la luminosidad emitida por el material calentado por el núcleo activo no es capaz de generar toda la luminosidad en el infrarrojo lejano, de tal forma que es necesario considerar la emisión del material calentado por la formación estelar.; ABSTRACT: We have obtained fluxes at various wavelengths for a sample of 43 quasars. Thanks to this information we have been able to build the sources' spectral energy distributions, which has allowed us to obtain the luminosities associated to star formation (in the far infrared) and the luminosities associated to their active galactic nuclei (in the UV-near infrared). This provided information in the contribution of both star formation and the active galactic nucleusto the total luminosity. We have qualitatively established that there is a relationship between de active nuclei luminosity and the luminosity in the far infrared. It has been found that the luminosity asociated to the material heated by the active nuclei is not able to explain all the luminosity in the far infrared...

What Do the Star Formation Histories of Galaxies Tell Us About the Starburst-AGN Connection?

Torres-Papaqui,J. P.; Coziol,R.; Plauchu-Frayn,I.; Andernach,H.; Ortega-Minakata,R. A.
Fonte: Instituto de Astronomía, UNAM Publicador: Instituto de Astronomía, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 EN
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We have determined the normal star formation histories (SFHs) for narrow emission line galaxies classified as star forming galaxies (SFGs), transition type objects (TOs), Seyfert 2s (Sy2s) and LINERs. The SFH varied with the activity type, following the mass of the galaxies and the importance of their bulge: LINERs reside in massive early-type galaxies, Sy2s and TOs in intermediate mass galaxies with intermediate morphological types, and SFGs are hosted in lower mass late-type spirals. Also, the maximum star formation rate in the past was found to increase with the virial mass within the aperture (VMA). This correlation suggests that the bulges and the supermassive black holes at the center of galaxies grow in parallel, in good agreement with the relation M BH-σ*.