377 research outputs found
GMOS Integral Field Spectroscopy of a Merging System with Enhanced Balmer Absorption
In this paper we present the three dimensional dynamics of the galaxy SDSS
J101345.39+011613.66, selected for its unusually strong Balmer absorption lines
(Wo(H-delta)=7.5A). Using the GMOS-South IFU in Nod & Shuffle mode we have
mapped the continuum and optical absorption lines of this z=0.1055 field
galaxy. This galaxy has a disturbed morphology, with a halo of diffuse material
distributed asymmetrically toward the north. Using the [OII] emission line
(Wo([OII])=4.1A) we find that the gas and hot OB stars are offset from the
older stars in the system. The gas also has a spatially extended and elongated
morphology with a velocity gradient of 100+/-20km/s across 6kpc in projection.
Using the strong H-gamma and H-delta absorption lines we find that the A- stars
are widely distributed across the system and are not centrally concentrated
arguing that the A-star population has formed in molecular clouds outside the
nucleus. By cross correlating the spectra from the datacube with an A-star
template we find evidence that the A-star population has a 40km/s shear in the
same direction as the gas. The disturbed morphology, strong colour gradients
and strong H-delta and H-gamma absorption lines in SDSS J101345.39 argue that
this is a recent tidal interaction/merger between a passive elliptical and
star-forming galaxy. Although based on a single object, these results show that
we can spatially resolve and constrain the dynamics of this short lived (yet
important) phase of galaxy formation in which the evolutionary process take
galaxies from star-forming to their quiescent end products.Comment: 7 pages, 7 figures. Accepted for publication in Ap
Spectral Mapping Reconstruction of Extended Sources
Three dimensional spectroscopy of extended sources is typically performed
with dedicated integral field spectrographs. We describe a method of
reconstructing full spectral cubes, with two spatial and one spectral
dimension, from rastered spectral mapping observations employing a single slit
in a traditional slit spectrograph. When the background and image
characteristics are stable, as is often achieved in space, the use of
traditional long slits for integral field spectroscopy can substantially reduce
instrument complexity over dedicated integral field designs, without loss of
mapping efficiency -- particularly compelling when a long slit mode for single
unresolved source followup is separately required. We detail a custom
flux-conserving cube reconstruction algorithm, discuss issues of extended
source flux calibration, and describe CUBISM, a tool which implements these
methods for spectral maps obtained with ther Spitzer Space Telescope's Infrared
Spectrograph.Comment: 11 pages, 8 figures, accepted by PAS
Differential Microlensing Measurements of Quasar Broad Line Kinematics in Q2237+0305
The detailed workings of the central engines of powerful quasars remain a
mystery. This is primarily due to the fact that, at their cosmological
distances, the inner regions of these quasars are spatially unresolvable.
Reverberation mapping is now beginning to unlock the physics of the Broad
Emission Line Region (BELR) in nearby, low-luminosity quasars, however it is
still unknown whether this gas is dominated by virial motion, by outflows, or
infall. The challenge is greater for more distant, powerful sources due to the
very long response time of the BELR to changes in the continuum. We present a
new technique for probing the kinematic properties of the BELR and accretion
disk of high-z quasars using differential microlensing, and show how
substantial information can be gained through a single observation of a
strongly-lensed quasar using integral field spectroscopy. We apply this
technique to GMOS IFU observations of the multiply-imaged quasar Q2237+0305,
and find that the observed microlensing signature in the CIII] broad emission
line favours gravitationally-dominated dynamics over an accelerating outflow.Comment: 16 pages, 14 figure
A systematic cross-search for radio/infrared counterparts of XMM-Newton sources
We present a catalog of cross-correlated radio, infrared and X-ray sources
using a very restrictive selection criteria with an IDL-based code developed by
us. The significance of the observed coincidences was evaluated through Monte
Carlo simulations of synthetic sources following a well-tested protocol. We
found 3320 coincident radio/X-ray sources with a high statistical significance
characterized by the sum of error-weighted coordinate differences. For 997 of
them, 2MASS counterparts were found. The percentage of chance coincidences is
less than 1%. X-ray hardness ratios of well-known populations of objects were
used to provide a crude representation of their X-ray spectrum and to make a
preliminary diagnosis of the possible nature of unidentified X-ray sources. The
results support the fact that the X-ray sky is largely dominated by Active
Galactic Nuclei at high galactic latitudes (|b| >= 10^\circ). At low galactic
latitudes (|b| <= 10^\circ) most of unidentified X-ray sources (~94%) lie at
|b| <= 2^\circ. This result suggests that most of the unidentified sources
found toward the Milky Way plane are galactic objects. Well-known and
unidentified sources were classified in different tables with their
corresponding radio/infrared and X-ray properties. These tables are intended as
a useful tool for researchers interested in particular identifications.Comment: Accepted for publication in Ap&SS. 47 pages, 10 figures. On-line
material: figures and table
Promover a fluĂȘncia em leitura: um estudo com alunos do 2Âș ano de escolaridade
Neste artigo são analisados os resultados de um Programa de Promoção da
FluĂȘncia em Leitura (PPFL), implementado junto de 74 alunos do 2Âș ano
de escolaridade de um Agrupamento Escolar do norte de Portugal. O PPFL
Ă© constituĂdo por 22 sequĂȘncias didĂĄticas, elaboradas a partir de 22 textos
(9 narrativos, 4 informativos e 9 poemas). Cada sequĂȘncia foi operacionalizada
em sessÔes de 10 a 15 minutos, durante 22 semanas, em ciclos
de cinco dias (quinta-feira a quarta-feira). Em cada semana foi trabalhado
apenas uma sequĂȘncia didĂĄctica (i.e. um texto). Foi utilizado um design
quase experimental, com grupo experimental e grupo de controlo e com pré
e pĂłs-teste. Os sujeitos foram avaliados atravĂ©s de um teste de fluĂȘncia de
leitura â o Teste de FluĂȘncia em Leitura (TFL) â, considerando as variĂĄveis
velocidade e precisão. Os resultados evidenciam diferenças significativas
a favor do grupo experimental, que superou as diferenças iniciais que se
registavam no pré-teste. A anålise qualitativa do impacto do PPFL aponta
para um incremento na motivação para ler, no envolvimento da famĂlia e
para a mudança de prĂĄticas por parte dos professores envolvidos.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), PortugalFundos Nacionais atravĂ©s da FCT (Fundação para a CiĂȘncia e a Tecnologia) e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) atravĂ©s do COMPETE 2020 â Programa Operacional Competitividade e Internacionalização (POCI) no Ăąmbito do CIEC (Centro de Investigação em Estudos da Criança, da Universidade do Minho) com a referĂȘncia POCI-01-0145-FEDER-00756
The detection and X-ray evolution of galaxy groups at high redshift
We describe some of the first X-ray detections of groups of galaxies at high
redshifts (z~0.4), based on the UK deep X-ray survey of McHardy et al (1998).
Combined with other deep ROSAT X-ray surveys with nearly complete optical
identifications, we investigate the X-ray evolution of these systems. We find
no evidence for evolution of the X-ray luminosity function up to z=0.5 at the
low luminosities of groups of galaxies and poor clusters (Lx>3e42 erg/s),
although the small sample size precludes very accurate measurements. This
result confirms and extends to lower luminosities current results based on
surveys at brighter X-ray fluxes. The evolution of the X-ray luminosity
function of these low luminosity systems is more sensitive to the thermal
history of the intra-group medium (IGM) than to cosmological parameters. Energy
injection into the IGM (from for example supernovae or AGN winds) is required
to explain the X-ray properties of nearby groups. The observed lack of
evolution suggests that the energy injection occured at redshifts z>0.5.Comment: 13 pages, MNRAS accepte
The History of Galaxy Formation in Groups: An Observational Perspective
We present a pedagogical review on the formation and evolution of galaxies in
groups, utilizing observational information from the Local Group to galaxies at
z~6. The majority of galaxies in the nearby universe are found in groups, and
galaxies at all redshifts up to z~6 tend to cluster on the scale of nearby
groups (~1 Mpc). This suggests that the group environment may play a role in
the formation of most galaxies. The Local Group, and other nearby groups,
display a diversity in star formation and morphological properties that puts
limits on how, and when, galaxies in groups formed. Effects that depend on an
intragroup medium, such as ram-pressure and strangulation, are likely not major
mechanisms driving group galaxy evolution. Simple dynamical friction arguments
however show that galaxy mergers should be common, and a dominant process for
driving evolution. While mergers between L_* galaxies are observed to be rare
at z < 1, they are much more common at earlier times. This is due to the
increased density of the universe, and to the fact that high mass galaxies are
highly clustered on the scale of groups. We furthermore discus why the local
number density environment of galaxies strongly correlates with galaxy
properties, and why the group environment may be the preferred method for
establishing the relationship between properties of galaxies and their local
density.Comment: Invited review, 16 pages, to be published in ESO Astrophysics
Symposia: "Groups of Galaxies in the Nearby Universe", eds. I. Saviane, V.
Ivanov, J. Borissov
Astronomical Spectroscopy
Spectroscopy is one of the most important tools that an astronomer has for
studying the universe. This chapter begins by discussing the basics, including
the different types of optical spectrographs, with extension to the ultraviolet
and the near-infrared. Emphasis is given to the fundamentals of how
spectrographs are used, and the trade-offs involved in designing an
observational experiment. It then covers observing and reduction techniques,
noting that some of the standard practices of flat-fielding often actually
degrade the quality of the data rather than improve it. Although the focus is
on point sources, spatially resolved spectroscopy of extended sources is also
briefly discussed. Discussion of differential extinction, the impact of
crowding, multi-object techniques, optimal extractions, flat-fielding
considerations, and determining radial velocities and velocity dispersions
provide the spectroscopist with the fundamentals needed to obtain the best
data. Finally the chapter combines the previous material by providing some
examples of real-life observing experiences with several typical instruments.Comment: An abridged version of a chapter to appear in Planets, Stars and
Stellar Systems, to be published in 2011 by Springer. Slightly revise
Optical Identification of the ASCA Medium Sensitivity Survey in the Northern Sky: Nature of Hard X-ray-selected Luminous Active Galactic Nuclei
We present the results of optical spectroscopic identifications of a bright
subsample of 2-10keV hard X-ray selected sources from the ASCA Medium
Sensitivity Survey in the northern sky. The flux limit of the subsample is
3*10^-13 erg s^-1 cm^-2 in the 2-10keV band. All but one of the 87 hard X-ray
selected sources are optically identified, with AGNs, 7 clusters of galaxies,
and 1 galactic star. It is the largest complete sample of hard X-ray selected
AGNs at the bright flux limit. Amounts of absorption to their nuclei are
estimated to be hydrogen column densities (N_H) of up to ~3*10^23 cm^-2 from
their X-ray spectra. Optical properties of X-ray absorbed AGNs with N_H >
1*10^22 cm^-2 indicate the effects of dust absorption: at redshifts, z<0.6,
AGNs without broad H\beta emission lines have significantly larger N_H value
than AGNs with broad H\beta emission lines. At z>0.6, the X-ray absorbed AGNs
have a large hard X-ray to optical flux ratio (log f2-10keV/fR > +1). However,
three X-ray absorbed z>0.6 AGNs show strong broad lines. In combination with
hard X-ray selected AGN samples from the ASCA Large Sky Survey, the ASCA Deep
Survey in the Lockman Hole and Chandra Deep Field North, the luminosity
distributions of absorbed and less-absorbed AGNs are compared.Comment: 56 pages with 14 figures. Accepted to ApJS. Fig.1 and tables are
available from http://www.subaru.naoj.org/staff/akiyama/papers/papers.htm
Far Infrared Observations of Radio Quasars and FR II Radio Galaxies
We report MIPS photometry of 20 radio-loud quasars and galaxies at 24 and 70
um (and of five at 160 um). We combine this sample with additional sources
detected in the far infrared by IRAS and ISO for a total of 47 objects,
including 23 steep spectrum Type I AGNs: radio-loud quasars and broad line
radio galaxies; and 24 Type II AGNs: narrow line and weak line FR II radio
galaxies. Of this sample, the far infrared emission of all but 3C 380 appears
to be dominated by emission by dust heated by the AGN and by star formation.
The AGN appears to contribute more than 50% of the far infrared luminosity in
most of sources. It is also expected that the material around the nucleus is
optically thin in the far infrared. Thus, the measurements at these wavelengths
can be used to test the orientation-dependent unification model. As predicted
by the model, the behavior of the sources is consistent with the presence of an
obscuring circumnuclear torus; in fact, we find it may still have significant
optical depth at 24 um.In addition, as expected for the radio-loud quasars,
there is a significant correlation between the low frequency radio (178 MHz)
and the 70 um emission, two presumably isotropic indicators of nuclear
activity. This result is consistent with the simple unified scheme. However,
there is a population of radio galaxies that are underluminous at 70 um
compared with the radio-loud quasars and hence are a challenge to the simple
unified model.Comment: Accepted for publication in ApJ, 33 pages, 7 figure
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