Observational Evidence Against Long-Lived Spiral Arms in Galaxies

Abstract

We test whether the spiral patterns apparent in many large disk galaxies should be thought of as dynamical features that are stationary in a co-rotating frame for > t_{dyn}, as implied by the density wave approach for explaining spiral arms. If such spiral arms have enhanced star formation (SF), observational tracers for different stages of the SF sequence should show a spatial ordering, from up-stream to downstream in the corotating frame: dense HI, CO, tracing molecular hydrogen gas, 24 micron emission tracing enshrouded SF and UV emission tracing unobscured young stars. We argue that such a spatial ordering should be reflected in the angular cross-correlation (CC, in polar coordinates) using all azimuthal positions among pairs of these tracers; the peak of the CC should be offset from zero, in different directions inside and outside the corotation radius. Recent spiral SF simulations by Dobbs & Pringle, show explicitly that for the case of a stationary spiral arm potential such angular offsets between gas and young stars of differing ages should be observable as cross-correlation offsets. We calculate the angular cross-correlations for different observational SF sequence tracers in 12 nearby spiral galaxies, drawing on a data set with high quality maps of the neutral gas HI, THINGS), molecular gas (CO, HERACLES) along with 24 micron emission (Spitzer, SINGS); we include FUV images (GALEX) and 3.6 $\mu$m emission (Spitzer, IRAC) for some galaxies, tracing aging stars and longer timescales. In none of the resulting tracer cross-correlations for this sample do we find systematic angular offsets, which would be expected for a stationary dynamical spiral pattern of well-defined pattern speed. This result indicates that spiral density waves in their simplest form are not an important aspect of explaining spirals in large disk galaxies.

13 pages, 16 figures

References in corpus (7)

• The GALEX Ultraviolet Atlas of Nearby Galaxies
• The formation of molecular clouds in spiral galaxies
• Kinematics of Spiral Arm Streaming in M51
• Geometrically Derived Timescales for Star Formation in Spiral Galaxies
• Arm & Interarm Star Formation in Spiral Galaxies
• Simulations of spiral galaxies with an active potential: molecular cloud formation and gas dynamics
• Instabilities of Spiral Shocks -- II. A quasi-steady State in the multi-phase inhomogeneous ISM

Cited by in corpus (68)

• PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• Dawes Review 4: Spiral Structures in Disc Galaxies
• The PdBI Arcsecond Whirlpool Survey (PAWS). I. A Cloud-Scale/Multi-Wavelength View of the Interstellar Medium in a Grand-Design Spiral Galaxy
• Self-Perpetuating Spiral Arms in Disk Galaxies
• Gas Kinematics on GMC scales in M51 with PAWS: cloud stabilization through dynamical pressure
• The dynamics of stars around spiral arms
• Dynamics of Non-Steady Spiral Arms in Disk Galaxies
• Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias
• Dynamics of stars around spiral arms in an N-body/SPH simulated barred-spiral galaxy
• The properties of the local spiral arms from RAVE data: two-dimensional density wave approach
• Spirals in galaxies
• On the galaxy spiral arms' nature as revealed by rotation frequencies
• Offset between stellar spiral arms and gas arms of the Milky Way
• Gas and Stellar Motions and Observational Signatures of Co-Rotating Spiral Arms
• Hic sunt dracones: Cartography of the Milky Way spiral arms and bar resonances with Gaia Data Release 2
• The Sun was not born in M 67
• Search For Star Cluster Age Gradients Across Spiral Arms of Three LEGUS Disk Galaxies
• Galaxy Zoo: Unwinding the Winding Problem - Observations of Spiral Bulge Prominence and Arm Pitch Angles Suggest Local Spiral Galaxies are Winding
• Dependence of Spiral Arms Pitch Angle on Wavelength as a Test of Density Wave Theory
• Characteristics of Spiral Arms in Late-type Galaxies
• Spiral and bar driven peculiar velocities in Milky Way sized galaxy simulations
• Interlocking Resonance Patterns in Galaxy Disks
• Gas and Star Formation in the Circinus Galaxy
• The prevalence of star formation as a function of Galactocentric radius
• Wide-field 12CO (J = 1-0) Imaging of the Nearby Barred Galaxy M83 with NMA and Nobeyema 45-m telescope: Molecular Gas Kinematics and Star Formation Along the Bar
• Numerical Simulations of Bubble-Induced Star Formation in Dwarf Irregular Galaxies with a Novel Stellar Feedback Scheme
• Systematic Variations of CO J=2-1/1-0 Ratio in The Barred Spiral Galaxy M83
• Star formation in grand-design, spiral galaxies. Young, massive clusters in the near-infrared
• Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms
• Geometric Offsets Across Spiral Arms in M51: Nature of Gas and Star Formation Tracers
• The role of spiral arms in Milky Way star formation
• Galaxy Zoo: star-formation versus spiral arm number
• Radial distributions of arm-gas offsets as an observational test of spiral theories
• How do different spiral arm models impact the ISM and GMC population?
• Spiral arm formation mechanisms: Spiral Structure in Barred galaxies. Observational constraints to spiral arm formation mechanisms
• The Swift/UVOT catalogue of NGC4321 star forming sources: A case against density wave theory
• Testing Density Wave Theory with Resolved Stellar Populations around Spiral Arms in M81
• Investigating the Origins of Spiral Structure in Disk Galaxies through a Multiwavelength Study
• Signatures of long-lived spiral patterns
• Feathering Instability of Spiral Arms. II. Parameter Study
• Young stars as tracers of a barred-spiral Milky Way
• Precision determination of corotation radii in galaxy disks: Tremaine-Weinberg v. Font-Beckman for NGC 3433
• Determining the Co-Rotation Radii of Spiral Galaxies Using Spiral Arm Pitch Angle Measurements at Multiple Wavelengths
• Spiral instabilities: Mode saturation and decay
• Distribution and kinematics of 26Al in the Galactic disc
• Dynamical effect of gas on spiral pattern speed in galaxies
• The local spiral arm in the LAMOST-Gaia common stars?
• Spiral arms and disc stability in the Andromeda galaxy
• Evidence in favour of density wave theory through star formation history maps and spatially resolved stellar clusters
• The Radcliffe Wave as the gas spine of the Orion Arm
• Classifying and modelling spiral structures in hydrodynamic simulations of astrophysical discs
• The origin of the structure of large-scale magnetic fields in disc galaxies
• Understanding the secular evolution of NGC 628 using UVIT
• Parallax-based Distances to Galactic Hii Regions: Nearby Spiral Structure
• Stellar Orbital Studies in Normal Spiral Galaxies I: Restrictions to the Pitch Angle
• The shock-induced star formation sequence resulting from a constant spiral pattern speed
• The Observed Age Gradient in the Milky Way -- as a Test for theories of spiral arm structure
• A SOFIA Survey of [CII] in the galaxy M51 II. [CII] and CO kinematics across spiral arms
• Stellar Orbital Studies in Normal Spiral Galaxies II: Restrictions to Structural and Dynamical parameters on Spiral Arms
• Resonance coupling in spiral arms: Patterns for flat rotation curve
• A Comprehensive Analysis on the Nature of the Spiral Arms in NGC 3686, NGC 4321, and NGC 2403
• Star formation in galaxies: the role of spiral arms
• Star formation rates and the kinematics of gas in the spiral arms of NGC 628
• Stellar Motion around Spiral Arms: Gaia Mock Data
• Effect of dark matter halo on global spiral modes in a collisionless galactic disc
• A Dynamic Galaxy: Stellar Age Patterns Across the Disk of M101
• Insights into the structure and kinematics of a Milky Way-like galaxy