Spirals in Galaxies and Large Surveys by Prof. Karen Masters

Jun 25, 2024

Lecture Notes: Spiries and Galaxy Surveys by Professor Karen Masters

Introduction

  • Presenter: Prof. Karen Masters, Haverford College, Pennsylvania
  • Background: Extragalactic astronomy, large surveys, galaxy morphology
  • Focus: Spirals in galaxies

Historical Background

  • First Observation of Spirals: Lord Rosse's Whirlpool Galaxy sketch (1800s)
  • Hubble's Tuning Fork: Classification of galaxies into elliptical and spirals, introduced the concept of galactic bars
  • Modern Classification: More nuanced, includes various spiral types, such as flocculent and grand-design spirals

Basics of Spiral Galaxies

  • Types:
    • Hubble’s System: Sa (large bulges, tight arms) to Sc (small bulges, loose arms)
    • DVA System: Flocculent (patchy) vs. Grand Design (symmetrical, well-defined arms)
  • Mathematical Model: Logarithmic spirals, characterized by constant pitch angles
  • Density Waves: Spirals as regions of higher star density; can be caused or influenced by interactions, bars, and internal instabilities

Recent Findings about Spiral Galaxies

  • Evidence suggests spirals are density waves, but they might also be winding up over time
  • Galactic Bars: Higher likelihood of two spiral arms
  • Simulations: Show spirals as self-excited instabilities

Observational Data from Large Surveys

  • Major Surveys: SDSS, DECaLS, Hubble, UKIDSS, and upcoming surveys like J-PAS and JADES
  • Role of Citizen Science: Galaxy Zoo project allows public to classify galaxies
  • **Galaxy Zoo Contributions: **Participants have made substantial contributions to the classification of galaxy images. Ensured data integrity through statistical validation and consistency checks.

Findings from Galaxy Zoo

  • Pitch Angle vs. Bulge Size: No clear correlation for most galaxies; slight differences noted when considering bars and color-mass segregation
  • Impact on Star Formation: Higher star formation rates in spiral arms; correlated with arm winding and other galaxy properties

Manga Data and Spectroscopy

  • Manga IFS Survey: Enables 2D spectroscopy of galaxies
  • Key Properties Mapped: Gas and stellar kinematics, H-alpha emission, stellar age, and metallicity

Detailed Morphology Insights

  • Gradient Analysis: Differences in star formation and metal distribution linked to spiral features and surrounding environment
  • Spiral Masking: Applied citizen science to map and analyze spiral arms in spectroscopy data
  • Star Formation Excess: Further evidence that star-forming regions are concentrated within spiral arms

Summary and Future Questions

  • **Key Points: **Spirals as density waves, potential for winding, discrepancies in isolated galaxies, and relationships between arms and stellar properties
  • **Ongoing Work: **Further investigation into spiral arm influence on galaxy evolution, enhanced analysis techniques leveraging both citizen science and computational methods

References for Further Reading

  • Publications and data from surveys like SDSS, DECaLS, and MAGNA
  • Galaxy Zoo project results and methodologies

Thank you [End of Lecture]