Uncertainties in the Deprojection of the Observed Bar Properties

Abstract

In observations, it is important to deproject the two fundamental quantities characterizing a bar, i.e., its length ($a$) and ellipticity ($e$), to face-on values before any careful analyses. However, systematic estimation on the uncertainties of the commonly used deprojection methods is still lacking. Simulated galaxies are well suited in this study. We project two simulated barred galaxies onto a 2D plane with different bar orientations and disk inclination angles ($i$). Bar properties are measured and deprojected with the popular deprojection methods in the literature. Generally speaking, deprojection uncertainties increase with increasing $i$. All the deprojection methods behave badly when $i$ is larger than $60^{\circ }$, due to vertical thickness of the bar. Thus, future statistical studies of barred galaxies should exclude galaxies more inclined than $60^{\circ }$. At moderate inclination angles ($i\le 60^{\circ }$), 2D deprojection methods (analytical and image stretching) and Fourier-based methods (Fourier decomposition and bar-interbar contrast) perform reasonably well with uncertainties $\sim 10\%$ in both the bar length and ellipticity. Whereas the uncertainties of the 1D analytical deprojection can be as high as $100\%$ in certain extreme case. We find that different bar measurement methods show systematic differences in the deprojection uncertainties. We further discuss the deprojection uncertainty factors with the emphasis on the most important one, i.e., the 3D structure of the bar itself. We construct two triaxial toy bar models that can qualitatively reproduce the results of the 1D and 2D analytical deprojections; they confirm that the vertical thickness of the bar is the main source of uncertainties.

arXiv comment11 pages, 18 figures, accepted for publication in ApJ

References in corpus (44)

• Secular Evolution and the Formation of Pseudobulges in Disk Galaxies
• What determines the strength and the slowdown rate of bars ?
• The Frequency of Barred Spiral Galaxies in the Near-IR
• Morphology, photometry and kinematics of N-body bars. I Three models with different halo central concentrations
• The Secular Evolution of Disk Structural Parameters
• Evolution of the Bar Fraction in COSMOS: Quantifying the Assembly of the Hubble Sequence
• A Near-Infrared Study of 2MASS Bars in Local Galaxies: An Anchor for High Redshift Studies
• Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation
• Nested and Single Bars in Seyfert and Non-Seyfert Galaxies
• The population of barred galaxies in the local universe I. Detection and characterisation of bars
• Galaxy Zoo: Bars in Disk Galaxies
• Dynamical Friction and the Distribution of Dark Matter in Barred Galaxies
• Secular Evolution Via Bar-Driven Gas Inflow: Results from BIMA SONG
• Two Red Clumps and the X-Shaped Milky Way Bulge
• Characterizing Bars at z~0 in the optical and NIR: Implications for the Evolution of Barred Disks with Redshift
• The Influence of Bars on Nuclear Activity
• Spiral arms, bar shape and bulge microlensing in the Milky Way
• The Split Red Clump of the Galactic Bulge from OGLE-III
• Bar Evolution Over the Last Eight Billion Years: A Constant Fraction of Strong Bars in GEMS
• The Nature of Boxy/Peanut-Shaped Bulges in Spiral Galaxies
• How Large Are the Bars in Barred Galaxies?
• Bars in Disk-Dominated and Bulge-Dominated Galaxies at z~0: New Insights from ~3600 SDSS Galaxies
• A Dust-Penetrated Classification Scheme for Bars as Inferred from their Gravitational Force Fields
• The structure of the Galactic bar
• Modelling the Galactic bar using OGLE-II Red Clump Giant Stars
• The Compression of Dark Matter Halos by Baryonic Infall
• Measurement of fast bars in a sample of early-type barred galaxies
• K-Band Observations of Boxy Bulges. I. Morphology and Surface Brightness Profiles
• Secular Evolution and Structural Properties of Stellar Bars in Galaxies
• A New Photometric Model of the Galactic Bar using Red Clump Giants
• An Imaging Survey of Early-Type Barred Galaxies
• Peanuts at an Angle: Detecting and Measuring the Three-Dimensional Structure of Bars in Moderately Inclined Galaxies
• Bars rejuvenating bulges? Evidence from stellar population analysis
• Barred Galaxies at z > 0.7: NICMOS HDFN Observations
• Bar Diagnostics in Edge-On Spiral Galaxies. I. The Periodic Orbits Approach
• The Carnegie-Irvine Galaxy Survey. II. Isophotal Analysis
• Gaseous Structures in Barred Galaxies: Effects of the Bar Strength
• Dependence of Barred Galaxy Fraction on Galaxy Properties and Environment
• Hot Disks And Delayed Bar Formation
• Near-Infrared Surface Photometry of a Sample of Barred Galaxies
• Fabry-Perot Absorption-Line Spectroscopy of NGC 7079: Kinematics and Bar Pattern Speed
• Homogenization of the Stellar Population along Late-Type Spiral Galaxies
• The Vertical X-shaped Structure in the Milky Way: Evidence from a Simple Boxy Bulge Model
• The stellar mass distribution in early-type disk galaxies: surface photometry and bulge-disk decompositions

Cited by in corpus (20)

• Debris Disks: Structure, Composition, and Variability
• Characterization of galactic bars from 3.6 $\mu$m S${}^4$G imaging
• SDSS-IV MaNGA: the indispensable role of bars in enhancing the central star formation of low-$z$ galaxies
• Bar effect on gas-phase abundance gradients. I. Data sample and chemical abundances
• SDSS-IV MaNGA: Bar pattern speed estimates with the Tremaine-Weinberg method and their error sources
• Galaxy Zoo: Finding offset discs and bars in SDSS galaxies
• The Effect of Bulge Mass on Bar Pattern Speed in Disk Galaxies
• Effects of Inner Halo Angular Momentum on the Peanut/X-shapes of Bars
• SDSS IV MaNGA: Bar pattern speed in Milky Way Analogue galaxies
• Deconstructing double-barred galaxies in 2D and 3D. I. Classical nature of the dominant bulges
• Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30m
• Near-Infrared Imaging of Barred Halo Dominated Low Surface Brightness Galaxies
• GalMod: a Galactic synthesis population model
• Deconstructing double-barred galaxies in 2D and 3D. II. Two distinct groups of inner bars
• The intrinsic three-dimensional shape of galactic bars
• Unraveling Joint Evolution of Bars, Star Formation, and Active Galactic Nuclei of Disk Galaxies
• Modelling Dark Matter Halo Spin using Observations and Simulations: application to UGC 5288
• Discovery of a near-infrared bar and a pseudobulge in the collisional ring galaxy Cartwheel
• On the Correlation Between Atomic Gas and Bars in Galaxies
• Deprojection of external barred galaxies from photometry