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We investigate the dynamical effects of a molecular cloud complex with a mass of about 10**7 M_sun and a size of a few 100 pc on the vertical distribution of stars and atomic hydrogen gas in a spiral galactic disc. Such massive complexes…

Astrophysics · Physics 2009-11-07 Chanda J. Jog , Chaitra A. Narayan

We demonstrate that in N-body simulations of isolated disc galaxies there is numerical vertical heating which slowly increases the vertical velocity dispersion and the disc thickness. Even for models with over a million particles in a disc,…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 S. A. Rodionov , N. Ya. Sotnikova

We present deep optical long-slit spectra of 17 edge-on spiral galaxies of intermediate to late morphological type, mostly parallel to their major axes and in a few cases parallel to the minor axes.The line-of-sight stellar kinematics are…

Astrophysics · Physics 2009-11-10 M. Kregel , P. C. van der Kruit , K. C. Freeman

We present observations and models of the kinematics and distribution of neutral hydrogen (HI) in the superthin galaxy FGC 1440 with an optical axial ratio $a/b = 20.4$. Using the Giant Meterwave Radio telescope (GMRT), we imaged the galaxy…

We explored a method to reconstruct the distribution function of the Galactic thick disc within the action space where nearby thick-disc stars are distributed. By applying this method to 127 chemically-selected thick-disc stars in the Solar…

Astrophysics of Galaxies · Physics 2015-09-30 Kohei Hattori , Gerard Gilmore

We study the properties of galaxies with very thin discs using a sample of 85 objects whose stellar disc radial-to-vertical scale ratio determined from photometric decomposition, exceeds nine. We present evidences of similarities between…

Astrophysics of Galaxies · Physics 2016-12-06 D. V. Bizyaev , S. J. Kautsch , N. Ya. Sotnikova , V. P. Reshetnikov , A. V. Mosenkov

We present spectroscopic observations of the stellar motions in the disk of the superthin edge-on spiral galaxy IC 5249 and re-analyse synthesis observations of the HI. We find that the HI rotation curve rises initially to about 90-100…

Astrophysics · Physics 2009-11-07 P. C. van der Kruit , J. Jimenez-Vicente , M. Kregel , K. C. Freeman

We describe how to estimate the velocity dispersions of ultra diffuse galaxies, UDGs, using a previously defined galaxy scaling relationship. The method is accurate for the two UDGs with spectroscopically measured dispersions, as well as…

Astrophysics of Galaxies · Physics 2017-02-22 Dennis Zaritsky

Having to have low thermal energy, the molecular gas in galaxies is expected to settle in a thin disc near the midplane. However, contradicting this understanding, recent studies have revealed considerably thick molecular discs in nearby…

Astrophysics of Galaxies · Physics 2020-04-29 Narendra Nath Patra

Ionized gas and stellar kinematical parameters have been measured along the major axis of 20 nearby disc galaxies. We discuss the properties of each sample galaxy distinguishing between those characterized by regular or peculiar kinematics.…

We present the Galactic model parameters for thin disc estimated by Sloan Digital Sky Survey (SDSS) data of 14 940 stars with apparent magnitudes $16<g_{o}\leq21$ in six intermediate latitude fields in the first Galactic quadrant.…

Astrophysics · Physics 2009-11-11 S. Bilir , S. Karaali , S. Ak , E. Yaz , E. Hamzaoglu

Nearly 400 Tycho-2 stars have been observed in a 720 square degree field in the direction of the North Galactic Pole with the high resolution echelle spectrograph ELODIE. Absolute magnitudes, effective temperatures, gravities and…

Astrophysics · Physics 2009-11-07 C. Soubiran , O. Bienaymé , A. Siebert

The kinematic dispersions of disc stars can be used to measure the dynamic contributions of baryons to the rotation curves of spiral galaxies and hence to trace the amount and distribution of the remaining dark matter. However, the simple…

Astrophysics of Galaxies · Physics 2017-05-31 Frederic V. Hessman

We theoretically study the vertical structure of the edge-on low surface brightness (LSB) galaxy UGC 7321. This is one of the few well-observed LSBs. We modeled it as a gravitationally coupled disk system of stars and atomic hydrogen gas in…

Astrophysics of Galaxies · Physics 2019-08-30 Suchira Sarkar , Chanda J. Jog

Most of the visible mass in a typical spiral galaxy is distributed in a thin disk, with a radial extent much larger than its thickness. While the planar disk structure, including non-axisymmetric features such as spiral structure, has been…

Astrophysics of Galaxies · Physics 2025-07-04 Chanda J. Jog

The stellar velocity dispersion, $\sigma$, is a quantity of crucial importance for spiral galaxies, where it enters fundamental dynamical processes such as gravitational instability and disc heating. Here we analyse a sample of 34 nearby…

Astrophysics of Galaxies · Physics 2019-09-25 Keoikantse Moses Mogotsi , Alessandro B. Romeo

In this first paper in a series we present a study of the global dust emission distribution in nearby edge-on spiral galaxies. Our sample consists of 16 angularly large and 13 less spatially resolved galaxies selected from the DustPedia…

To calibrate stellar velocity dispersion measurements from optical and near-IR stellar lines, and to improve the black hole mass (MBH)- stellar velocity dispersion (sigma) relation, we measure stellar velocity dispersions based on high…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Wol-Rang Kang , Jong-Hak Woo , Andreas Schulze , Dominik A. Riechers , Sang Chul Kim , Daeseong Park , Vernesa Smolcic

The opacity of spiral galaxies is examined by modelling the dust and stellar content of individual galaxies. The model is applied to five late-type spiral galaxies (NGC 4013, IC 2531, UGC 1082, NGC 5529 and NGC 5907). Having analyzed a…

Astrophysics · Physics 2009-09-25 E. M. Xilouris , Y. I. Byun , N. D. Kylafis , E. V. Paleologou , J. Papamastorakis

Disk galaxies viewed as thin planar structures resulting from the conservation of angular momentum of an initially rotating pre-galactic cloud allow merely a first-order model of galaxy formation. Still, the presence of vertically extended…