236 research outputs found
Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of H emission
line of a sample of 111 spiral galaxies with recognizable and well defined
spiral morphology and with a well determined environmental status, ranging from
isolation to non-disruptive interaction with satellites or companions. The form
and properties of the rotation curves are considered as a function of the
isolation degree, morphological type and luminosity. The line ratios are used
to estimate the metallicity of all the detected HII regions, thus producing a
composite metallicity profile for different types of spirals. We have found
that isolated galaxies tend to be of later types and lower luminosity than the
interacting galaxies. The outer parts of the rotation curves of isolated
galaxies tend to be flatter than in interacting galaxies, but they show similar
relations between global parameters. The scatter of the Tully-Fisher relation
defined by isolated galaxies is significantly lower than that of interacting
galaxies. The [NII]/H ratios, used as metallicity indicator, show a
clear trend between Z and morphological type, t, with earlier spirals showing
larger ratios; this trend is tighter when instead of t the gradient of the
inner rotation curve, G, is used; no trend is found with the interaction
status. The Z-gradient of the disks depends on the type, being almost flat for
early spirals, and increasing for later types. The [NII]/H ratios
measured for disk HII regions of interacting galaxies are higher than for
normal/isolated objects, even if all the galaxy families present similar
distributions of H Equivalent Width.Comment: accepted for publication in A&A (tables for HII region parameters
incomplete, contact [email protected] for the whole set of tables
The Cerebellar Dopaminergic System
In the central nervous system (CNS), dopamine (DA) is involved in motor and cognitive functions. Although the cerebellum is not been considered an elective dopaminergic region, studies attributed to it a critical role in dopamine deficit-related neurological and psychiatric disorders [e.g., Parkinson's disease (PD) and schizophrenia (SCZ)]. Data on the cerebellar dopaminergic neuronal system are still lacking. Nevertheless, biochemical studies detected in the mammalians cerebellum high dopamine levels, while chemical neuroanatomy studies revealed the presence of midbrain dopaminergic afferents to the cerebellum as well as wide distribution of the dopaminergic receptor subtypes (DRD1-DRD5). The present review summarizes the data on the cerebellar dopaminergic system including its involvement in associative and projective circuits. Furthermore, this study also briefly discusses the role of the cerebellar dopaminergic system in some neurologic and psychiatric disorders and suggests its potential involvement as a target in pharmacologic and non-pharmacologic treatments
Isolated galaxies: residual of primordial building blocks?
CONTEXT.The mass assembly is believed to be the dominant process of early
galaxy formation. This mechanism of galaxy building can proceed either by
repeated major mergers with other systems, or by means of accretion of matter
from the surrounding regions. AIMS.In this paper we compare the properties of
local disk galaxies that appear isolated, i.e. not tidally affected by other
galaxies during the last few Gyr within the volume given by cz<= 5000 km/s,
with those galaxies at z values from 0.25 to 5.
METHODS.Effective radii for 203 isolated galaxies and 1645 galaxies from the
RC3 have been collected and the two samples have been analyzed statistically. A
similar comparison has been made with half light radii studied at high z from
the literature.
RESULTS.We found that isolated galaxies are in general smaller than other
present epoch galaxies from the RC3. We notice the lack of systems larger than
7 kpc among them. Their size distribution appears to be similar to that of
galaxies at 1.4 <= z <= 2. The models of the merging history also indicate that
the isolated galaxies did stop their merging process at about that redshift,
evolving passively since then. The galaxy density seems to have remained
unchanged since that epoch.
CONCLUSIONS.Isolated galaxies appears to be the end products of the merging
process as proposed in the hierarchical accretion scenario at around z=1.4. For
this class of galaxies this was the last significant merging event in their
lives and have evolved passively since then. This is confirmed by the
analytical estimate of the merging fraction with z and by the comparison with
sizes of distant galaxies.Comment: 6 pages, 3 figures. Accepted for publication in A&A. A&A style file
added to the sourc
Stars & Gas in the Galaxy Pair II Zw 70/71
II Zw 71 (UGC 9562) was classified as a ``probable'' polar-ring galaxy in the
Polar-Ring Catalog, based upon its optical appearance. We present 21 cm and
optical observations of this galaxy and its companion, the blue star-forming
dwarf II Zw 70. Our 21 cm observations show that 5e8 solar masses of HI is
present in a polar ring orbiting II Zw 71, and show a spatially and
kinematically contiguous streamer with 2.5e8 solar masses of HI gas between the
two galaxies. This gaseous bridge, plus our observations of Halpha line
emission in the polar ring and in II Zw 70, are strong evidence for an ongoing
interaction between the two galaxies. However, the configuration of the
streamer suggests that the polar ring itself may well have predated the current
interaction, which then stimulated an outburst of star formation in the ring
gas.Comment: 24 pages, 7 figures; submitted to A
Cultural adaptation and psychometric validation of the Caring Efficacy scale in a sample of Italian nurses
Caring is the essence of nursing practice. Caring Efficacy scale was developed with the purpose of measuring nurses' perceived self-efficacy in orienting and maintaining caring relationships with patients. Since any instruments measuring caring self-efficacy have not been developed in Italy, the study aimed at culturally adapting and validating Caring Efficacy scale in a sample of Italian nurses. A total of 300 registered nurses were asked to fill a self-reported questionnaire; translation-back-translation procedure was carried out to maintain semantic, idiomatic and conceptual equivalence of the original scale. Then, factor analysis was performed in order to test appropriateness of the factor structure. Convergent and discriminant validity was also tested. A two-factor structure with 17 items was found. Results show that Cronbach's Alpha value was 0.84 for Confidence to Care, and 0.75 for Doubts and Concerns. Correlation analysis for convergent and discriminant validity showed that Confidence to Care was positively correlated with sense of coherence and no significant correlation with Doubts and Concerns was found. Caring efficacy scale can be used by nurse managers as a way of assessing nurses' self-efficacy and their caring orientation, thus improving quality of patient care
Muscular collision chess:A qualitative exploration of the role and development of cognition, understanding and knowledge in elite-level decision making
Decision making (DM) is a crucial part of team invasion games. The role of context and how this drives both the initial DM and primes in-action planning and execution, termed contextual priors, has been investigated. Findings suggest a significant role for cognition, which appears to run contrary to some of the suggestions made by an ecological dynamics approach. Wishing to clarify this situation for coaches and psychologists, this research explores the experience of nine top-tier key decision makers in rugby union, using an interview approach. Results showed a wide range of context-based information considered by players during the DM process. Furthermore, this information acted to prime subsequent attention and in-action thinking. Finally, this research sought to understand if, and therefore how, DM could be taught, developed and primed by players and coaches. Our data are supportive of a more cognitively focused approach to developing DM although our data do not dismiss a role for direct perception in optimising performance. Implications for practice are discussed
2D Spectroscopy of Candidate Polar-Ring Galaxies: I. The Pair of Galaxies UGC 5600/09
Observations of the pair of galaxies VV 330 with the SCORPIO multimode
instrument on the 6-m Special Astrophysical Observatory telescope are
presented. Large-scale velocity fields of the ionized gas in H-alfa and
brightness distributions in continuum and H-alfa have been constructed for both
galaxies with the help of a scanning Fabry Perot interferometer. Long-slit
spectroscopy is used to study the stellar kinematics. Analysis of the data
obtained has revealed a complex structure in each of the pair components. Three
kinematic subsystems have been identified in UGC 5600: a stellar disk, an inner
gas ring turned with respect to the disk through ~80degrees, and an outer gas
disk. The stellar and outer gas disks are noncoplanar. Possible scenarios for
the formation of the observed multicomponent kinematic galactic structure are
considered, including the case where the large-scale velocity field of the gas
is represented by the kinematic model of a disk with a warp. The velocity field
in the second galaxy of the pair, UGC 5609, is more regular. A joint analysis
of the data on the photometric structure and the velocity field has shown that
this is probably a late-type spiral galaxy whose shape is distorted by the
gravitational interaction, possibly, with UGC 5600.Comment: 18 pages, 6 figure
A Search for Very Extended Ionized Gas in Nearby Starburst and Active Galaxies
We report the results from a pilot study of 10 nearby starburst and active
galaxies conducted with the Taurus Tunable Filter (TTF) on the Anglo-Australian
and William Herschel Telescopes. The main purpose of this imaging survey is to
search for warm emission-line gas on the outskirts (galactocentric distances R
> 10 kpc) of galaxies to provide direct constraints on the size and geometry of
the ``zone of influence'' of these galaxies on their environment. Gaseous
complexes or filaments larger than ~ 20 kpc are discovered or confirmed in six
of the galaxies in the sample (NGC 1068, NGC 1482, NGC 4388, NGC 6240, NGC
7213, and MR 2251-178). Slightly smaller structures are seen for the first time
in the ionization cones and galactic winds of NGC 1365, NGC 1705, Circinus
galaxy, and ESO484-G036. The TTF data are combined with new optical long-slit
spectra as well as published and archived radio and X-ray maps to constrain the
origin and source of ionization of these filaments. A broad range of phenomena
is observed, including large-scale ionization cones and galactic winds, tidal
interaction, and ram-pressure stripping by an intracluster medium. The source
of ionization in this gas ranges from shock ionization to photoionization by
the central AGN or in-situ hot young stars. The sample is too small to draw
statistically meaningful conclusions about the extent and properties of the
warm ionized medium on large scale and its relevance to galaxy formation and
evolution. The next generation of tunable filters on large telescopes promises
to improve the sensitivity to faint emission-line fluxes at least tenfold and
allow systematic surveys of a large sample of emission-line galaxies.Comment: 17 pages + 20 gif figures (high-resolution color version of these gif
figures will be available with the electronic version of the published
paper). Accepted for publication in the Astronomical Journal, November 2003
issu
The growth of the central region by acquisition of counterrotating gas in star-forming galaxies
Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counterrotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counterrotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars
- âŠ