scholarly journals The Building of Galactic Disks: Insights from the Triangulum Spiral Galaxy Messier 33

2006 ◽  
Vol 2 (S235) ◽  
pp. 29-35
Author(s):  
David L. Block ◽  
Ivânio Puerari ◽  
Giovanni G. Fazio ◽  
Alan Stockton ◽  
Gabriela Canalizo ◽  
...  
Keyword(s):  
Spiral Galaxy ◽  
Open Systems ◽  
Galactic Disk ◽  
Carbon Star ◽  
Absorption Bands ◽  
V Band ◽  
Outer Disk ◽  
Radial Profiles ◽  
The Galaxy ◽  
Low Metallicity

AbstractThe Triangulum Spiral Galaxy Messier 33 offers unique insights into the building of a galactic disk. We identify spectacular arcs of intermediate age (0.6 Gyr − 2 Gyr) stars in the low-metallicity outer disk. The northern arc spans ~120 degrees in azimuth and up to 5 arcmin in width. The arcs are located 2-3 disk scale lengths from the galaxy centre (where 1 disk scale length is equivalent to 0.1 degrees in the V-band) and lie precisely where there is a warp in the HI profile of M33. Warps and infall are inextricably linked (Binney, 1992). We present spectroscopy of candidate stars in the outer northern arc, secured using the Keck I telescope in Hawaii. The target stars have estimated visual magnitudes as faint as V~ 25m. Absorption bands of CN are seen in all spectra reported in this review talk, confirming their carbon star status. Also presented are PAH emissivity radial profiles generated from IRAC observations of M33 using the Spitzer Space Telescope. A dramatic change of phase in the m = 2 Fourier component is detected at the domain of the arcs. M33 serves as an excellent example how the disks of spiral galaxies in our Universe are built: as dynamically open systems, growing from the inward, outward.

scholarly journals A Search for Galactic Carbon Stars

1988 ◽  
Vol 108 ◽  
pp. 48-49
Author(s):  
Hideo Mabhara
Keyword(s):  
Galactic Plane ◽  
Carbon Star ◽  
Spectral Features ◽  
Spectral Classification ◽  
Carbon Stars ◽  
Schmidt Telescope ◽  
Infrared Wavelength ◽  
V Band ◽  
The Galaxy ◽  
Objective Prism

The carbon star is one of the best probes for the galactic study; (1)it is intrinsically bright (Mbol = − 2 to − 6) especially in the red and infrared wavelength regions,(2)it has spectral features readily detectable on objective prism plates due to their strong carbon molecular bands,(3)it is an evolved star distributed abundantly (∼1 star per square degree) along the galactic plane.We can detect it in the Galaxy up to several kpc from the sun on objective prism plates of the Schmidt telescope.We have been making survey observations of faint cool carbon stars using the Kiso 105-cm Schmidt telescope. Kodak IN and 103aF plates are respectively taken behind the 4-degree objective prism (700 Åmm−1 at Hα) for the detection and for the spectral classification. V-band plates are utilized to obtain the position and the brightness of the stars detected.The survey areas are distributed along the northern galactic plane. Seven fields in the Cassiopeia region (l = 115° to 133° and eight fields in the Taurus-Auriga-Gemini region (i = 170° to 188°) have been observed and processed up to now (Maehara and Soyano 1987a,b).

scholarly journals Bimodal chemical evolution of the Galactic disk and the Barium abundance of Cepheids

2013 ◽  
Vol 9 (S298) ◽  
pp. 86-91 ◽  
Author(s):  
Jacques R.D. Lépine ◽  
Sergei Andrievky ◽  
Douglas A. Barros ◽  
Thiago C. Junqueira ◽  
Sergio Scarano
Keyword(s):  
Chemical Evolution ◽  
Star Formation Rate ◽  
Galactic Disk ◽  
Formation Rate ◽  
Abundance Distribution ◽  
The Galaxy ◽  
Low Metallicity ◽  
The Difference ◽  
Two Sides ◽  
High Metallicity

AbstractIn order to understand the Barium abundance distribution in the Galactic disk based on Cepheids, one must first be aware of important effects of the corotation resonance, situated a little beyond the solar orbit. The thin disk of the Galaxy is divided in two regions that are separated by a barrier situated at that radius. Since the gas cannot get across that barrier, the chemical evolution is independent on the two sides of it. The barrier is caused by the opposite directions of flows of gas, on the two sides, in addition to a Cassini-like ring void of HI (caused itself by the flows). A step in the metallicity gradient developed at corotation, due to the difference in the average star formation rate on the two sides, and to this lack of communication between them. In connection with this, a proof that the spiral arms of our Galaxy are long-lived (a few billion years) is the existence of this step. When one studies the abundance gradients by means of stars which span a range of ages, like the Cepheids, one has to take into account that stars, contrary to the gas, have the possibility of crossing the corotation barrier. A few stars born on the high metallicity side are seen on the low metallicity one, and vice-versa. In the present work we re-discuss the data on Barium abundance in Cepheids as a function of Galactic radius, taking into account the scenario described above. The [Ba/H] ratio, plotted as a function of Galactic radius, apparently presents a distribution with two branches in the external region (beyond corotation). One can re-interpret the data and attribute the upper branch to the stars that were born on the high metallicity side. The lower branch, analyzed separately, indicates that the stars born beyond corotation have a rising Barium metallicity as a function of Galactic radius.

scholarly journals Two uneven sisters

2018 ◽  
Vol 620 ◽  
pp. A108
Author(s):  
B. Vollmer ◽  
C. Pappalardo ◽  
M. Soida ◽  
A. Lançon
Keyword(s):  
Spiral Galaxy ◽  
Galactic Disk ◽  
Pressure Profile ◽  
Galactic Structure ◽  
Virgo Cluster ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Free Region ◽  
Ram Pressure ◽  
The Galaxy

Since the Virgo cluster is the closest galaxy cluster in the northern hemisphere, galaxy interactions can be observed in it at kiloparsec resolution. The spiral galaxy NGC 4388 underwent a ram-pressure stripping event ∼200 Myr ago caused by its highly eccentric orbit within the Virgo cluster. This galaxy fulfills all diagnostic criteria for having undergone active ram-pressure stripping in the recent past: it has a strongly truncated HI and Hα disk, an asymmetric ridge of polarized radio continuum emission, extended extraplanar gas toward the opposite side of the ridge of polarized radio continuum emission, and has undergone a recent (a few hundred million years ago) quenching of its star formation activity in the outer, gas-free galactic disk. We made dynamical simulations of the ram-pressure stripping event to investigate the influence of galactic structure on the observed properties of NGC 4388. The combination of a deep optical spectrum of the outer gas-free region of the galactic disk together with deep HI, Hα, far-ultraviolet, and polarized radio continuum data allows us to constrain numerical simulations to derive the temporal ram-pressure profile, the three-dimensional velocity vector of the galaxy, and the time since peak ram pressure with a high level of confidence. From the simulations, an angle between the ram-pressure wind and the galactic disk of 30° is derived. The galaxy underwent peak ram pressure ∼240 Myr ago. The observed asymmetries in the disk of NGC 4388 are not caused by the present action of ram pressure, but by the resettling of gas that has been pushed out of the galactic disk during the ram-pressure stripping event. For the detailed reproduction of multi-wavelength observations of a spiral galaxy that undergoes or underwent a ram-pressure stripping event, galactic structure, such as spiral arms for example, must be taken into account.

Bipolar outflow of gas in the spiral galaxy NGC 3079

1986 ◽  
Vol 64 (4) ◽  
pp. 531-535 ◽  
Author(s):  
Nebojsa Duric ◽  
E. R. Seaquist
Keyword(s):  
Spectral Index ◽  
Spiral Galaxy ◽  
Central Region ◽  
Qualitative Description ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Bipolar Outflow ◽  
The Galaxy

Very large array, radio-continuum observations of the edge-on spiral galaxy NGC 3079 are presented. The observations reveal that the nucleus has windlike properties and that the central region of the galaxy exhibits an unusual figure-eight morphology that shows evidence of severe depolarization and a flattening spectral index away from the nucleus. A qualitative description of a model is presented to account for the observed radio properties. It is shown that a wind-driven shock propagating away from the nucleus and focused by the ambient disk gas can give rise to the observed morphology.

scholarly journals Li isotopes in metal-poor halo dwarfs: a more and more complicated story

2009 ◽  
Vol 5 (S268) ◽  
pp. 201-210
Author(s):  
Monique Spite ◽  
François Spite
Keyword(s):  
Cosmic Rays ◽  
Big Bang ◽  
The Other ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
The Galaxy ◽  
Li Isotope ◽  
Low Metallicity ◽  
The Big Bang ◽  
Early Galaxy

AbstractThe nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li?

scholarly journals The Evolution of 3He, 4He and D in the Galaxy

2000 ◽  
Vol 198 ◽  
pp. 540-546 ◽  
Author(s):  
Cristina Chiappini ◽  
Francesca Matteucci
Keyword(s):  
Chemical Evolution ◽  
Present Model ◽  
Galactic Disk ◽  
The Sun ◽  
Mixing Process ◽  
Low Mass Stars ◽  
A Value ◽  
The Galaxy ◽  
Low Mass ◽  
Standing Problem

In this work we present the predictions of a modified version of the ‘two-infall model’ (Chiappini et al. 1997 - CMG) for the evolution of 3He, 4He and D in the solar vicinity, as well as their distributions along the Galactic disk. In particular, we show that when allowing for extra-mixing process in low mass stars (M < 2.5 M⊙), as predicted by Charbonnel and do Nascimento (1998), a long standing problem in chemical evolution is solved, namely: the overproduction of 3He by the chemical evolution models as compared to the observed values in the sun and in the interstellar medium. Moreover, we show that chemical evolution models can constrain the primordial value of the deuterium abundance and that a value of (D/H)p < 3 × 10—5 is suggested by the present model. Finally, adopting the primordial 4He abundance suggested by Viegas et al. (1999), we obtain a value for ΔY/ΔZ ≃ 2 and a better agreement with the solar 4He abundance.

scholarly journals Surface Photometry of Spiral Galaxy NGC 5005 and Elliptical Galaxy NGC 4278

2018 ◽  
Vol 15 (3) ◽  
pp. 314-323
Author(s):  
Baghdad Science Journal
Keyword(s):  
Spiral Galaxy ◽  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Surface Photometry ◽  
Contour Maps ◽  
Sky Survey ◽  
Flat Field ◽  
The Galaxy

Two galaxies have been chosen, spiral galaxy NGC 5005 and elliptical galaxy NGC 4278 to study their photometric properties by using surface photometric techniques with griz-Filters. Observations are obtained from the Sloan Digital Sky Survey (SDSS). The data reduction of all images have done, like bias and flat field, by SDSS pipeline. The overall structure of the two galaxies (a bulge, a disk), together with isophotal contour maps, surface brightness profiles and a bulge/disk decomposition of the galaxy images were performed, although the disk position angle, ellipticity and inclination of the galaxies have been estimated.

The Outer Disk of the Galaxy

1992 ◽  
pp. 399-399 ◽  
Author(s):  
Bruce W. Carney ◽  
Patrick Seitzer
Keyword(s):  
Outer Disk ◽  
The Galaxy

scholarly journals The strange case of the peculiar spiral galaxy NGC 5474

2020 ◽  
Vol 634 ◽  
pp. A124 ◽  
Author(s):  
M. Bellazzini ◽  
F. Annibali ◽  
M. Tosi ◽  
A. Mucciarelli ◽  
M. Cignoni ◽  
...  
Keyword(s):  
Old Age ◽  
Spiral Galaxy ◽  
The Other ◽  
Spiral Pattern ◽  
Stellar Content ◽  
Peculiar Star ◽  
Space Telescope ◽  
Stellar Disc ◽  
Star Forming ◽  
The Galaxy

We present the first analysis of the stellar content of the structures and substructures identified in the peculiar star-forming galaxy NGC 5474, based on Hubble Space Telescope resolved photometry from the LEGUS survey. NGC 5474 is a satellite of the giant spiral M 101, and it is known to have a prominent bulge that is significantly off-set from the kinematic centre of the underlying H I and stellar disc. The youngest stars (age ≲ 100 Myr) trace a flocculent spiral pattern extending out to ≳8 kpc from the centre of the galaxy. On the other hand, intermediate-age (age ≳ 500 Myr) and old (age ≳ 2 Gyr) stars dominate the off-centred bulge and a large substructure residing in the south-western part of the disc (SW over-density) and they are not correlated with the spiral arms. The old age of the stars in the SW over-density suggests that this may be another signature of any dynamical interactions that have shaped this anomalous galaxy. We suggest that a fly by with M 101, generally invoked as the origin of the anomalies, may not be sufficient to explain all the observations. A more local and more recent interaction may help to put all the pieces of this galactic puzzle together.

scholarly journals DDO68-V1: an extremely metal-poor LBV in a void galaxy

2018 ◽  
Vol 14 (S344) ◽  
pp. 392-395
Author(s):  
Yulia Perepelitsyna ◽  
Simon Pustilnik
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Rare Event ◽  
Local Universe ◽  
Hii Region ◽  
V Band ◽  
Star Evolution ◽  
Low Metallicity ◽  
Massive Star Evolution

AbstractThe lowest metallicity massive stars in the Local Universe with $Z\sim \left( {{Z}_{\odot }}/50-{{Z}_{\odot }}/30 \right)$ are the crucial objects to test the validity of assumptions in the modern models of very low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. DDO68-V1 in a void galaxy DDO68 is a unique extremely metal-poor massive star. Discovered by us in 2008 in the HII region Knot3 with $Z={{Z}_{\odot }}/35\,\left[ 12+\log \left( \text{O/H} \right)\sim 7.14 \right]$, DDO68-V1 was identified as an LBV star. We present here the LBV lightcurve in V band, combining own new data and the last archive and/or literature data on the light of Knot3 over the 30 years. We find that during the years 2008-2011 the LBV have experienced a very rare event of ‘giant eruption’ with V-band amplitude of 4.5 mag ($V\sim {{24.5}^{m}}-{{20}^{m}}$).

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