Star Formation and Stellar Phenomena in Our Galaxy
VLASS – Galactic Science
Life cycle of star formation in our Galaxy
as a proxy for understanding the Local
Universe
legacy science
Infrared GLIMPSE survey
VLASS – Galactic Science
Detailed study and Identification of High
Mass Star Formation Regions
•
high mass stars have a huge effect on their
environs, through UV radiation, wind energy,
shocks, enriching the ISM
•
our understanding of high mass star formation
is woefully incomplete: triggered star
formation vs. spontaneous collapse?
•
these stars drive winds and jets, which are
compact thermal sources
•
H II regions form once the star has contracted
down to the main sequence, and are useful
probes of high mass star formation
•
methanol masers are associated with regions
of high mass star formation
HST image of NGC 3603, showing a cluster
of massive star formation
GLIMPSE and CORNISH (5 GHz survey)
VLASS – Galactic Science
Detection of a previously unknown
planetary nebula from the CORNISH
survey, Hoare et al. (2012). Left: 5 GHz
Middle: Spitzer GLIMPSE (3.6,4.5,8 um)
Right: UKIDSS (JHK)
Stellar Winds, Planetary Nebulae, and Active Stars
•
thermal radio emission from
stellar winds
complements UV, optical studies
•
evolved OB stars reside in the densest part of the Galaxy
•
understanding mass loss
mass and energy flows in local Universe
•
PN have flat radio spectra in the GHz range (methanol masers reveal physical conditions)
•
only 3000 (of proposed 23,000) planetary nebula currently known (Frew & Parker 2010)
•
rates of detection and mass loss rates affect models for input energy into ISM
•
Magnetically active stars have flat radio spectra from non-thermal emission with possible
gyroresonance at higher frequencies; high spatial resolution enables identification
VLASS – Galactic Science
Setting the Landscape
Ku band survey is complementary with many other
survey efforts
VLASS – Galactic Science
example: constraining thermal sources
Typical spectral energy distribution of an Ultra-Compact HII
region (red curve). The distinctive shape is the product
of two emission processes: thermal radiation from warm
dust (the 'hump') and thermal free-free radio emission
from ionised gas (the 'plateau'). Fluxes normalized
With the proposed sensitivity,
radio emission can be used to
distinguish between these types
of thermal sources in star forming
regions Hoare et al. (2012)
radio loud UCHII regions
radio quiet Massive YSOs
CORNISH limited in scope!
sensitivity and spatial coverage
VLASS – Galactic Science
•
Key Science Advantages of Ku band
–
sensitivity is optimized to thermal sources (
> +0.6)
–
access to 12.2 GHz methanol maser (usually associated with 6.7 GHz
methanol maser and star formation) to help constrain pumping
mechanism; access to recombination lines
–
complementary with infrared and submillimeter surveys that trace dusty
regions of early and current star formation
–
picks up thermal emission from dense plasmas which are missed by lower
frequencies
•
Key Science Disadvantages of S band
–
baseline sensitivity of 30
Jy will not pick up the same population as the
baseline sensitivity at Ku band will: miss many optically thick, thermal
sources!
–
non-thermal (AGN) contamination will make source identification nature
very difficult at S-band
–
no spectral lines (methanol maser very important indicator of star forming
regions; recombination lines provide basic kinematics)
VLASS – Galactic Science
Parameters of Proposed Survey
Galactic Latitude Coverage
Delve into the fascinating realms of high mass star formation, stellar winds, planetary nebulae, and active stars through the VLASS Galactic Science project. This initiative leverages cutting-edge surveys like GLIMPSE and CORNISH to unlock the secrets of star birth, evolution, and their impact on the surrounding universe. From understanding the life cycle of stars to identifying thermal sources, the research sheds light on the complexities of our galactic neighborhood.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
E N D
Presentation Transcript
VLASS Galactic Science Life cycle of star formation in our Galaxy as a proxy for understanding the Local Universe legacy science Infrared GLIMPSE survey
VLASS Galactic Science Detailed study and Identification of High Mass Star Formation Regions high mass stars have a huge effect on their environs, through UV radiation, wind energy, shocks, enriching the ISM HST image of NGC 3603, showing a cluster of massive star formation our understanding of high mass star formation is woefully incomplete: triggered star formation vs. spontaneous collapse? these stars drive winds and jets, which are compact thermal sources H II regions form once the star has contracted down to the main sequence, and are useful probes of high mass star formation GLIMPSE and CORNISH (5 GHz survey) methanol masers are associated with regions of high mass star formation
VLASS Galactic Science Stellar Winds, Planetary Nebulae, and Active Stars thermal radio emission from stellar winds complements UV, optical studies evolved OB stars reside in the densest part of the Galaxy understanding mass loss mass and energy flows in local Universe PN have flat radio spectra in the GHz range (methanol masers reveal physical conditions) only 3000 (of proposed 23,000) planetary nebula currently known (Frew & Parker 2010) rates of detection and mass loss rates affect models for input energy into ISM Magnetically active stars have flat radio spectra from non-thermal emission with possible gyroresonance at higher frequencies; high spatial resolution enables identification Detection of a previously unknown planetary nebula from the CORNISH survey, Hoare et al. (2012). Left: 5 GHz Middle: Spitzer GLIMPSE (3.6,4.5,8 um) Right: UKIDSS (JHK)
VLASS Galactic Science Setting the Landscape Ku band survey is complementary with many other survey efforts
VLASS Galactic Science example: constraining thermal sources With the proposed sensitivity, radio emission can be used to distinguish between these types of thermal sources in star forming regions Hoare et al. (2012) radio loud UCHII regions radio quiet Massive YSOs CORNISH limited in scope! sensitivity and spatial coverage Typical spectral energy distribution of an Ultra-Compact HII region (red curve). The distinctive shape is the product of two emission processes: thermal radiation from warm dust (the 'hump') and thermal free-free radio emission from ionised gas (the 'plateau'). Fluxes normalized
VLASS Galactic Science Key Science Advantages of Ku band sensitivity is optimized to thermal sources ( > +0.6) access to 12.2 GHz methanol maser (usually associated with 6.7 GHz methanol maser and star formation) to help constrain pumping mechanism; access to recombination lines complementary with infrared and submillimeter surveys that trace dusty regions of early and current star formation picks up thermal emission from dense plasmas which are missed by lower frequencies Key Science Disadvantages of S band baseline sensitivity of 30 Jy will not pick up the same population as the baseline sensitivity at Ku band will: miss many optically thick, thermal sources! non-thermal (AGN) contamination will make source identification nature very difficult at S-band no spectral lines (methanol maser very important indicator of star forming regions; recombination lines provide basic kinematics)
VLASS Galactic Science Parameters of Proposed Survey
