H-alpha Images of Ultra-Flat Edge-On Spiral Galaxies

Abstract

We present the H$\alpha$ images of ultra-flat (UF) spiral galaxies seen practically edge-on. The galaxies have the angular diameter in the $B$ band $a>1.9^{\prime }$ and the apparent axial ratio $(a/b)>10$. We found that their H$\alpha$ images look, on average, almost two times thinner than those in the red continuum. The star-formation rate in the studied objects, determined from the H$\alpha$ flux, is in good agreement with that calculated from the $FUV$ flux from the GALEX survey if we use the modified Verheijen and Sancisi formula taking into account the internal extinction in the UF galaxies. The logarithm of the specific star-formation rate in the UF galaxies shows a small scatter, $0.19$, with a smooth decrease from $-10.4$ for dwarf spirals to $-10.7$ for massive ones. The relative amount of the hydrogen mass in UF disks varies from about 50\% in dwarf disks to about 8\% in massive ones. Structural distortions are less common in the UF galaxies (about 16\%) than those in thick (less isolated) disks of edge-on spiral galaxies. On the cosmic time scale, 13.7 Gyr, large spiral disks are more efficient "engines" for gas processing into stars than dwarf spirals.

arXiv comment19 pages, 2 tables, 8 figures

References in corpus (22)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Star Formation in Galaxies Along the Hubble Sequence
• The Optical and Near-Infrared Properties of Galaxies: I. Luminosity and Stellar Mass Functions
• 2MASS Extended Source Catalog: Overview and Algorithms
• HyperLEDA. III. The catalogue of extragalactic distances
• The GALEX Ultraviolet Atlas of Nearby Galaxies
• Comparison of H-alpha and UV Star Formation Rates in the Local Volume: Systematic Discrepancies for Dwarf Galaxies
• An H-alpha Imaging Survey of Galaxies in the Local 11 Mpc Volume
• The Ursa Major Cluster of Galaxies. IV ; HI synthesis observations
• A GALEX Ultraviolet Imaging Survey of Galaxies in the Local Volume
• The ALFALFA HI mass function: A dichotomy in the low-mass slope and a locally suppressed 'knee' mass
• Action Dynamics of the Local Supercluster
• On the Interstellar Medium and Star Formation Demographics of Galaxies in the Local Universe
• Why are some galaxy disks extremely thin?
• Morphological properties of galaxies in different Local Volume environments
• Halpha3: an Halpha imaging survey of HI selected galaxies from ALFALFA. V: The Coma Supercluster survey completion
• Global dust attenuation in disc galaxies: strong variation with specific star formation and stellar mass, and the importance of sample selection
• Ultra-Flat Galaxies Selected from RFGC Catalog. I. The Sample Properties
• Ultra-Flat Galaxies Selected from RFGC Catalog. II. Orbital Estimates of Halo Masses
• Ultra-Flat Galaxies Selected from RFGC Catalog. III. Star Formation Rate
• EIG - II. Intriguing characteristics of the most extremely isolated galaxies
• A reference sample of face-on bulgeless galaxies

Cited by in corpus (1)

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