2,030 research outputs found
An Origin of the Huge Far-Infrared Luminosity of Starburst Mergers
Recently Taniguchi and Ohyama found that the higher CO to CO
integrated intensity ratios at a transition =1--0, CO)CO) , in a sample of starburst merging
galaxies such as Arp 220 are mainly attributed to the depression of CO
emission with respect to CO. Investigating the same sample of galaxies
analyzed by Taniguchi & Ohyama, we find that there is a tight, almost linear
correlation between the dust mass and CO luminosity. This implies that
dust grains are also depressed in the high- starburst mergers, leading to
the higher dust temperature () in them because of the relative
increase in the radiation density. Nevertheless, the average dust mass () of the high- starburst mergers is higher significantly than that of
non-high galaxies. This is naturally understood because the galaxy mergers
could accumulate a lot of dust grains from their progenitor galaxies together
with supply of dust grains formed newly in the star forming regions. Since
(FIR) given the dust emissivity law, , the increases in both and
explain well why the starburst mergers are so bright in the FIR. We discuss
that the superwind activity plays an important role in destroying dust grains
as well as dense gas clouds in the central region of mergers.Comment: 10 pages (aaspp4.sty), 3 postscript figures (embedded). Accepted for
publication in Astrophysical Journal Letter
CO observations of southern mergers
There are good reasons to believe that the formation of some elliptical galaxies result from the merging of two disk galaxies, as Toomre and Toomre first suggested (1972, Ap. J. 178, 623). Such a process strongly enhances the star-formation activity of the system, thus consuming its molecular gas. This might account for the low cold-gas content of elliptical galaxies compared to that of spirals. Researchers present here CO(1-0) and CO(2-1) observations of a sequence of three objects, NGC 1614, NGC 3256, and NGC 7252, that present characteristic features of merger remnants: single body and extended tidal tails. NGC 3256 and 7252 even exhibit the r(exp 1/4) radial light distribution that is the signature of elliptical galaxies, which indicates that their stellar bodies are in late stages of relaxation. Both NGC 1614 and NGC 3256 undergo extended bursts of star formation revealed by their large far-infrared luminosities, and by the presence in the near-infrared spectrum of the 3.28 microns feature (Morwood: 1986, A. A. 166, 4) attributed to polycyclic aromatic hydrocarbons. On the other hand, NGC 7252 has a milder activity of star formation, as suggested by a lower infrared luminosity, and thus seems to have gone past the starburst phase. The CO data were collected with the Swedish-ESO 15 m Submillimeter Telescope (SEST) (beamsize = 43 seconds at 115 GHz, 23 seconds at 230 GHz). For NGC 7252, researchers have only observed the central position in CO-12(1-0). The spectrum is displayed together with an HI spectrum obtained with the Nancay radiotelescope. Researchers mapped NGC 1614 and NGC 3256 in CO-12(1-0) and CO-12(2-1), and also observed the nucleus of NGC 3256 in CO-13(1-0). The various CO spectra obtained towards the nuclei of both galaxies are presented. Characteristics of the galaxies are gathered, with luminosities and masses in solar units and temperatures in Kelvins
CO deficiency in galaxies of the Fornax cluster?
There is ample observational evidence that cluster galaxies are different from those in the field. Interaction with the hot intracluster medium affects the morphology of the galaxies, their gaseous content and possibly their star-formation activity. Tidal encounters between galaxies also play an important role. The atomic component has been investigated in detail for several clusters, among them our neighbor Virgo. With the Swedish-ESO 15 m telescope, we have observed in the 12CO(1-0) transition the 23 brightest spirals and lenticulars of the Formax cluster
Depression in Luminous Starburst Mergers
It is known that the class of luminous starburst galaxies tends to have
higher integrated line intensity ratios
() than normal spiral galaxies (). Since most previous studies
investigated only , it remains uncertain whether the luminous starburst
galaxies are overabundant in CO or underabundant in CO. Here we
propose a new observational test to examine this problem. Our new test is to
compare far-infrared luminosities [(FIR)] with those of CO and
and , respectively]. It is shown that there
is a very tight correlation between and L(FIR), as found in many
previous studies. However, we find that the CO luminosities of the
high-R galaxies are lower by a factor of three on the average than those
expected from the correlation for the remaining galaxies with ordinary
values. Therefore, we conclude that the observed high values for the
luminous starburst galaxies are attributed to their lower CO line
intensities.Comment: 9 pages (aaspp4.sty), 3 postscript figures (embedded). Accepted for
publication in Astrophysical Journal Letter
Materials and paint technique of a special masterpiece: Jacopo Tintoretto’s The Wedding Feast at Cana in Venice
The present paper illustrates the results of the scientific investigation performed on the painting on canvas The Wedding Feast at Cana (1561) by Jacopo Robusti, nicknamed Tintoretto. The painting, commissioned for the refectory of the Crociferi’s Convent of, is located in the Sacristy of the Basilica della Madonna della Salute in Venice, after the dissolution of the congregation.
Noninvasive single spot technique (X-ray fluorescence), and analytical investigations (optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, and gas chromatography coupled with mass spectrometry) on ten micro-samples were combined to retrieve the palette and identifying the organic binding media.
The investigations revealed the existence of many pigments available at that time in Venice, among which is the precious lapis lazuli. The identification of two pigments, one white and one blue, allowed to know the possible time of execution of the two angles, added at the top. The study of the painting has made it possible to know completely unexpected aspects: the painting does not present the traditional ground of gypsum and animal glue, but it turns out to be complete without the preparatory layer. This painting is described by art historians as an “oil on canvas”; however, GC/MS did not identify any fatty acids of siccative oil, but only egg, presumably yolk, then The Wedding Feast at Cana was made in tempera.
on canvas The Wedding Feast at Cana (1561) by Jacopo Robusti, nicknamed Tintoretto. The
painting, commissioned for the refectory of the Crociferi’s Convent of, is located in the Sacristy
of the Basilica della Madonna della Salute in Venice, after the dissolution of the congregation.
Noninvasive single spot technique (X-ray fluorescence), and analytical investigations (optical
microscopy, scanning electron microscopy with energy dispersive spectroscopy, and gas
chromatography coupled with mass spectrometry) on ten micro-samples were combined to
retrieve the palette and identifying the organic binding media. The investigations revealed the
existence of many pigments available at that time in Venice, among which is the precious lapis
lazuli. The identification of two pigments, one white and one blue, allowed to know the possible
time of execution of the two angles, added at the top. The study of the painting has made it
possible to know completely unexpected aspects: the painting does not present the traditional
ground of gypsum and animal glue, but it turns out to be complete without the preparatory
layer. This painting is described by art historians as an “oil on canvas”; however, GC/MS did
not identify any fatty acids of siccative oil, but only egg, presumably yolk, then The Wedding
Feast at Cana was made in tempera
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