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1.
Isabel Márquez Josefa Masegosa Mariano Moles Jesús Varela Daniella Bettoni Giusseppe Galletta 《Astrophysics and Space Science》2003,284(2):711-714
We present the study of long slit spectra in the region ofHα 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 (RC) are considered as a function
of the isolation degree, morphological type, t, 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 (ISO) tend to be of later types and lower luminosity than the interacting galaxies (INT). The outer parts
of the RC of ISO tend to be flatter than in INT, but they show similar relations between global parameters. The scatter of
the Tully-Fisher (TF) relation defined by ISO is significantly lower than that of INT. The [NII]/Hα ratios, used as a metallicity
indicator, show a clear trend between Z and t, with earlier spirals showing higher ratios; this trend is tighter when instead
of t the gradient of the inner RC, G, is used; no trend is found with the change in 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]/Hα ratios measured
for disk HII regions of INT are higher than for normal/ISO objects, even if all the galaxy families present similar distributions
of Hα Equivalent Width.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
K.G. Noeske P. Papaderos L.M. Cairós K.J. Fricke 《Astrophysics and Space Science》2003,284(2):615-618
We present deep Near-Infrared (NIR) imaging of Blue Compact Dwarf Galaxies (BCDs), allowing for the first time to derive and
systematize the NIR structural properties of their stellar low-surface brightness (LSB) host galaxies. Compared to optical
data, NIR images, being less contamined by the extended stellar and ionized gas emission from the starburst, permit to study
the LSB host galaxy closer to its center. We find that radial surface brightness profiles (SBPs) of the LSB hosts show at
large radii a mostly exponential intensity distribution, in agreement with previous optical studies. At small to intermediate
radii, however, the NIR data reveal an inwards flattening with respect to the outer exponential slope (`type V SBPs', Binggeli
and Cameron, 1991) in the LSB component of more than one half of the sample BCDs. This result may constitute an important
observational constraint to the dynamics and evolution of BCDs. We apply a modified exponential fitting function (Papaderos
et al., 1996a) to parametrize and systematically study type V profiles in BCDs. A Sérsic law is found to be less suitable
for studying the LSB component of BCDs, since it yields very uncertain solutions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
4.
Recent spectroscopic observations of galaxies in the Fornax-Cluster reveal nearly unresolved ‘star-like’ objects with red-shifts
appropriate to the Fornax-Cluster. These objects have intrinsic sizes of ≈ 100 pc and absolute B-band magnitudes in the range
- 14 < MB < -11.5 mag and lower limits for the central surface brightness μB ≥ 23 mag/arcsec2 (Phillipps et al., 2001, Hilker et al., 1999), and so appear to constitute a new population of ultra-compact dwarf galaxies
(UCDs). Such compact dwarfs were predicted to form from the amalgamation of stellar super-clusters (= clusters of star clusters;
not to confuse with super stellar clusters (SSC)) by P. Kroupa (1998), which are rich aggregates of young massive star clusters
(YMCs) that can form in collisions between gas-rich galaxies. Here we present the evolution of super-clusters in a tidal field.
The YMCs merge on a few super-cluster crossing times. Super-clusters that are initially as concentrated and massive as Knot
S in the interacting Antennae galaxies (Whitmore et al., 1999) evolve to merger objects that are long-lived and show properties
comparable to the newly discovered UCDs.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
5.
Jonathan Braine P.-A. Duc U. Lisenfeld V. Charmandaris O. Vallejo S. Leon E. Brinks 《Astrophysics and Space Science》2002,281(1-2):407-408
We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal
Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission.
These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between
two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of
gas and a bona fide galaxy. We have detected CO in 8 TDGs (Braine, Lisenfeld, Duc and Leon, 2000: Nature
403, 867; Braine, Duc, Lisenfeld, Charmandaris, Vallejo, Leon and Brinks: 2001, A&A
378, 51), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 108
M
⊙. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms
from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular
gas masses is observed, in accord with the transformation of HI into H2. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor ∼ 100) than
that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity (≳sim
1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily
inaccessible due to the extreme difficulty of measuring the molecular gas mass. The star formation efficiency, measured by
the CO luminosity per Hα flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of
these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although
uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and
we find that the ‘dynamical’ masses of TDGs, estimated from the CO line widths, seem not to be greater than the ‘visible’
masses (HI + H2 + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties,
we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark
matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that
they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the
ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas,
which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
6.
Results are presented from a detailed spectrophotometric study of a unique system of physically coupled galaxies whose spectra
contain identical emission lines. This system consists of four galaxies, three of which have a double or multiple structure
in their central portions and are, by definition, galaxies with two or multiple nuclei. Two of these objects are the galaxies
with an ultraviolet excess (UVE), Mark 261 and Mark 262, while one is a galaxy made up of two identical starlike nuclei that
are referred to as the “twin objects.” In the DSS2 charts, the latter show up as two adjacent stars without any surroundings.
However, there are two condensations between these starlike nuclei. The fourth object has a triplet structure. It is shown
here that all these objects have the same emission (line) spectra and red shifts. All the physical characteristics that can
be determined from the spectra are determined: red shifts, relative intensities of emission lines, their equivalent widths,
distances to the galaxies, etc. It is concluded that the members of this system have a common origin, more or less consistent
with Ambartsumyan's idea of the fragmentation of an isolated, high density body.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 503–514 (November 2005). 相似文献
7.
We study the spatial orientation of 5 169 galaxies that have radial velocity 3 000 to 5 000 km s−1. The ‘position angle–inclination’ method is used to find the spin vector and the projections of spin vector of the galaxy
rotation axes. The spatial isotropic distribution is assumed to examine the non-random effects. For this, we have performed
chi-square, Fourier, and auto-correlation tests. We found a random alignment of spin vectors of total galaxies with respect
to the equatorial coordinate system. The spin vector projections of total galaxies is found to be oriented tangentially with
respect to the equatorial center. The spiral galaxies show a similar orientation as shown by the total sample. Five subsamples
of barred spiral (late-type) galaxies show a preferred alignment. However, early-type barred spirals show a random orientation.
A weak morphological dependence is noticed in the subsamples of late type barred spirals. A comparison with the previous works
and the possible explanation of the results will be presented. 相似文献
8.
G. Hasinger J.-U. Fischer A. D. Schwope T. Boller J. Trümper W. Voges 《Astronomische Nachrichten》1997,318(6):329-334
We have selected a complete, flux-limited sample of bright point-like sources with absorbed X-ray spectra from the ROSAT All-Sky survey, the ROSAT Hard Survey (RHS). The sample is drawn from the high-galactic latitude sky, |bII| > ±30°, and avoids the general direction of the Magellanic Clouds and the Virgo Cluster. It comprises a total of 182 objects of which 118 were previosly catalogued objects and 64 were new AGN candidates. Through optical follow-up studies at La Silla, Calar Alto and the 6m Zelentchuk telescope we could identify 56 of the new objects, thus achieving a spectrscopic completeness of 96% of the sample. The selection strategy turned out to be extremely useful. Out of the new identifications, 84% are indeed active galaxies or emission line galaxies. While 14 objects are new BL Lac candidates 33 of the new AGN are Seyfert galaxies with a redshift distribution in the range 0.021–0.63, peaking at around 0.06, i.e. relatively local. Surprisingly, about 40% of the X-ray selected Seyfert galaxies seem to reside in interacting systems. With smaller selection uncertainties this fraction exceeds the number of paired galaxies in optically selected samples and therefore gives strong support to the idea that AGN activity is triggered by interaction. 相似文献
9.
P. Papaderos Y.I. Izotov K.G. Noeske L.M. Cairós N.G. Guseva T.X. Thuan K.J. Fricke 《Astrophysics and Space Science》2003,284(2):619-622
Using HST and ground-based optical and NIR imaging data, we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18
possesses an extended low-surface brightness (LSB) old stellar population underlying its star-forming (SF) regions. We show
that the exponential intensity decrease observed in the filamentary LSB envelope of the BCD out to 18″ (1.3 kpc at the adopted
distance of 15 Mpc) is not due to an evolved stellar disc, but rather due to extended ionized gas emission. Broad-band images
reveal, after subtraction of nebular line emission, a compact stellar LSB component extending slightly beyond the SF regions.
This stellar host, being blue over a radius range of 5 exponential scale lengths and showing little colour contrast to the
SF component, differs strikingly from the red LSB host of standard BCDs. This fact, in connection with the blue colours of
component I Zw 18 C (see discussion in Papaderos et al. 2002), suggests that most of the stellar mass in I Zw 18 has formed
within the last 0.5 Gyr. Furthermore, we show that the exponential intensity fall-off in the filamentary ionized envelope
of I Zw 18 is not particular to this system but a common property of the ionized halo of many SF dwarf galaxies on galactocentric
distances of several kpc. In the absence of an appreciable underlying stellar background, extended ionized gas emission dominates
in the periphery of I Zw 18, superficially resembling an exponential stellar disc on optical surface brightness profiles.
The case of I Zw 18 suggests caution in the search of more distant young galaxy candidates. Intense SF activity in the early
phase of dwarf galaxy formation may result in an extended ionized gas halo which can be mistaken for an evolved stellar disc
by studying only its exponential surface brightness profile.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
P. Augusto J. I. Gonzalez-Serrano A. C. Edge N. A. B. Gizani P. N. Wilkinson I. Perez-Fournon 《New Astronomy Reviews》1999,43(8-10)
We are conducting a multi-wavelength (radio, optical, and X-ray) observational campaign to classify, morphologically and physically, a sample of 55 flat-spectrum radio sources dominated by structure on kpc-scales. This sample contains 22 compact-/medium-sized symmetric object candidates, a class of objects thought to be in the early stages of the evolution of radio galaxies. The vast majority of the remaining objects have core-plus-one-sided-jet structures, half of which show sharply bent jets, probably due to strong interactions with the interstellar medium of the host galaxies. Once the observational campaign is completed, we will constrain evolutionary theories of radio galaxies at their intermediate stages and possibly understand the physics of the hypothesised narrow-line region in active galactic nuclei, given our advantageous statistical position. 相似文献
11.
We present the preliminary results for a sample of 21 high luminosity ULIRGs (LIR > 1012.3 L⊙), selected from the 1Jy sample. Based on R band imaging we have performed an analysis of their morphologies. The main
result obtained is that about half of the host galaxies are represented by spheroids and in the other half an exponential
disk has been detected or they show still trace of a merging process going on. Regarding the relation between morphology and
nuclear activity it seems that more advanced mergers appear in the most active galaxies. Hence the data support the evolutionary
scheme proposed by Sanders 15 years ago that ULIRGs can be the earliest precursors of optical QSOs.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
We report on the results of cross-correlation of a sample of 903 Utraluminous IRAS galaxies (ULIRGs) with the ROSAT-All Sky Survey Bright Source Catalogue and the ROSAT archived pointing observations. The sample of ULIRGs has been compiled from the recently released PSCz redshift survey. In total,35 ULIRGs are securely detected by the ROSAT All-Sky Survey and pointing observations, five of which are blazars. The statistical properties of these sources in the soft X-ray band are determined and compared with their properties on other wavebands. We find that the ratio of the soft X-ray to the far-infrared flux spans about five orders of magnitude and reaches values of about unity. This ratio is a good indicator of the main energy source of ULIRGs. Those with soft X-ray to far-infrared flux exceeding 0.01 are probably powered by accretion onto central supermassive black holes while those with ratios smaller than 0.001 are probably powered by starbursts or other heating processes, or are Compton thick sources. Some ULIRGs have energy contributions from both. This ratio is low for most ULIRGs and hyperluminous infrared galaxies, which explains their low detection rate by ROSAT and ASCA.We also find that some ULIRGs have a similar soft X-ray luminosity vs. temperature relation to that for groups of galaxies and elliptical galaxies,suggesting a common origin of these systems. Our study also reveals a tight correlation between the hardness ratio and the soft X-ray luminosity for Seyfert 1s/QSOs. 相似文献
13.
Eline Tolstoy 《Astrophysics and Space Science》2003,284(2):579-588
The smallest dwarf galaxies are the most straight forward objects in which to study star formation processes on a galactic
scale. They are typically single cell star forming entities, and as small potentials in orbit around a much larger one they
are unlikely to accrete much (if any) extraneous matter during their lifetime (either intergalactic gas, or galaxies) because
they will typically lose the competition with the much larger galaxy. We can utilise observations of stars of a range of ages
to measure star formation and enrichment histories back to the earliest epochs. The most ancient objects we have ever observed
in the Universe are stars found in and around our Galaxy. Their proximity allows us to extract from their properties detailed
information about the time in the early Universe into which they were born. A currently fashionable conjecture is that the
earliest star formation in the Universe occurred in the smallest dwarf galaxy sized objects. Here I will review some recent
observational highlights in the study of dwarf galaxies in the Local Group and the implications for understanding galaxy formation
and evolution.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
We discuss the properties of the galaxies in about 60 rich, nearby clusters, using kinematic data from the ESO Nearby Abell
Cluster Survey, combined with new imaging data. The images were used to classify the galaxies, and to recalibrate the galaxy
types derived from the ENACS spectra; this yields galaxy-type estimates for about4800 galaxies. For about 1200 galaxies, a
bulge/disk decomposition could be made, which yields sizes and luminosities of bulges and disks. From the projected radial
distances and relative l.o.s.-velocities we derived the galaxy ensembles with significantly different phase-space distributions.
We find that galaxies in and outside substructure must be distinguished. The morphological composition of the substructures
appears to vary with projected radius. Outside substructures, 4 galaxy ensembles must be defined: viz. the brighest Es, the
other early-type galaxies, the early spirals(Sa-Sb), and the late spirals (including the emission-line galaxies). We also
study the morphology-density relation, and we find that the segregation of the late spirals is driven mostly by global factors,
while the segregation of Es, S0s and early spirals is driven mostly by local density. The properties of early spirals and
S0ssupport the picture in which early spirals transform into S0s, while the properties of the late spirals do not support
such a relation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Jochen Heidt Immo Appenzeller Armin Gabasch Klaus Jäger Stella Seitz The FDF-Team 《Astrophysics and Space Science》2003,284(2):385-388
The FORS Deep Field project is a multi-colour, multi-object spectroscopical investigation of a ∼ 7′ × ′' region near the south
galactic pole based mostly on observations carried out with the FORS instruments attached to the VLT telescopes. It includes
the QSO Q 0103-260 (z = 3.36). The goal of this study is to improve our understanding of the formation and evolution of galaxies
in the young Universe. In this contribution, the photometric observations are presented. In particular, a combined B and I
selected UBgRIJKs photometric catalog of 8753 objects in the FDF is presented and its content is briefly described. The formal
50% completeness limits for point sources, derived from the coadded images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and
21.57in U, B, g, R, I, J and Ks, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
Javier Graciá-Carpio Santiago García-Burillo Pere Planesas 《Astrophysics and Space Science》2008,313(1-3):331-335
The sample of nearby LIRGs and ULIRGs for which dense molecular gas tracers have been measured is building up, allowing for
the study of the physical and chemical properties of the gas in the variety of objects in which the most intense star formation
and/or AGN activity in the local universe is taking place. This characterisation is essential to understand the processes
involved, discard others and help to interpret the powerful starbursts and AGNs at high redshift that are currently being
discovered and that will routinely be mapped by ALMA. We have studied the properties of the dense molecular gas in a sample
of 17 nearby LIRGs and ULIRGs through millimeter observations of several molecules (HCO+, HCN, CN, HNC and CS) that trace different physical and chemical conditions of the dense gas in these extreme objects. In
this paper we present the results of our HCO+ and HCN observations. We conclude that the very large range of measured line luminosity ratios for these two molecules severely
questions the use of a unique molecular tracer to derive the dense gas mass in these galaxies. 相似文献
17.
R. A. Kandalyan 《Astrophysics》2005,48(1):99-110
Radio observations with the VLA-A radio telescope of 30 OH megamaser galaxies at a frequency of 1.49 GHz are discussed. Radio emission was detected from all 30 of these galaxies. Radio emission was detected from 5 of the 30 objects for the first time. Important results were obtained for 12 galaxies that had previously been little studied in the radio continuum. Additional data at 1.49 GHz were obtained for the remaining 13 objects. The core component of the continuum radio emission predominates in the OH megamaser galaxies.Translated from Astrofizika, Vol. 48, No. 1, pp. 125–138 (February 2005). 相似文献
18.
Results of spectral observations of 45 objects from the BIG sample (corresponding to 35 IRAS sources) obtained on the 2.6-m
telescope at the BAO are reported. Emission lines are observed for 42 galaxies, 1 object is an absorption galaxy, and 2 turned
out to be stars. The red shifts are determined, the radial velocities, distances, sizes, and absolute stellar magnitudes are
calculated, the parameters of the spectral lines are determined, the objects are classified according to their activity type,
and the IR and far IR luminosities are calculated. Of the 42 emission galaxies, 1 was type Sy2, 2 were LINERs, 1 was an AGN
(Sy2 or LINER), 4 were composite, 25 were HII (including 6 with nuclear star-formation activity), and 9 were Em of undetermined
type (3 of which may be AGN). Calculations show that 23 of the objects are LIG. A physical coupling is discovered for 9 multiple
systems. Spectra of some of the galaxies are shown.
__________
Translated from Astrofizika, Vol. 49, No. 1, pp. 23–40 (February 2006). 相似文献
19.
Major-mergeing pairs of galaxies are excellent experimental objects to study the simultaneous influences of galaxy itself and the external environment, which can be traced by the changes of star formation rates. These effects, including the stellar mass of galaxies, the projected distance, and the relative inclination of pairs of galaxies, are all important factors related to star formation rates. The results imply that the galaxies with the greater star formation rates tend to be caused by the greater stellar masses, and the galaxies with relative inclinations close to parallel also have greater increases about star formation. However, the projected distances have no correlation with the star formation rates in the scope of this study. 相似文献
20.
E. Noordermeer M. A. W. Verheijen 《Monthly notices of the Royal Astronomical Society》2007,381(4):1463-1472
We study the location of massive disc galaxies on the Tully–Fisher (TF) relation. Using a combination of K -band photometry and high-quality rotation curves, we show that in traditional formulations of the TF relation (using the width of the global H i profile or the maximum rotation velocity), galaxies with rotation velocities larger than 200 km s−1 lie systematically to the right of the relation defined by less massive systems, causing a characteristic 'kink' in the relations. Massive, early-type disc galaxies in particular have a large offset, up to 1.5 mag, from the main relation defined by less massive and later-type spirals.
The presence of a change in slope at the high-mass end of the TF relation has important consequences for the use of the TF relation as a tool for estimating distances to galaxies or for probing galaxy evolution. In particular, the luminosity evolution of massive galaxies since z ≈ 1 may have been significantly larger than estimated in several recent studies.
We also show that many of the galaxies with the largest offsets have declining rotation curves and that the change in slope largely disappears when we use the asymptotic rotation velocity as kinematic parameter. The remaining deviations from linearity can be removed when we simultaneously use the total baryonic mass (stars + gas) instead of the optical or near-infrared luminosity. Our results strengthen the view that the TF relation fundamentally links the mass of dark matter haloes with the total baryonic mass embedded in them. 相似文献
The presence of a change in slope at the high-mass end of the TF relation has important consequences for the use of the TF relation as a tool for estimating distances to galaxies or for probing galaxy evolution. In particular, the luminosity evolution of massive galaxies since z ≈ 1 may have been significantly larger than estimated in several recent studies.
We also show that many of the galaxies with the largest offsets have declining rotation curves and that the change in slope largely disappears when we use the asymptotic rotation velocity as kinematic parameter. The remaining deviations from linearity can be removed when we simultaneously use the total baryonic mass (stars + gas) instead of the optical or near-infrared luminosity. Our results strengthen the view that the TF relation fundamentally links the mass of dark matter haloes with the total baryonic mass embedded in them. 相似文献