Anne Buckner
Career Stage
Postdoctoral Researcher
Poster Abstract
INDICATE is a powerful new tool employing a novel approach to provide a quantitative measure of the clustering behaviours of individual objects in a dataset within a user-defined parameter space. As such it can be used in a wide array of applications to perform rigorous spatial analyses. In this poster we show that when combined with kinematic data from Gaia DR2 INDICATE can be used to study the star formation history of a cluster in a robust way. Applying the tool to NGC2264, we find the dynamic and spatial behaviours of Young Stellar Object (YSO) members at different evolutionary stages are distinct. Our results suggest (i) dynamical evolution is responsible for the present YSO distributions, (ii) prolonged star formation has been occurring sequentially in the cluster, and (iii) stellar feedback from the cluster’s massive O-type binary, S Mon, is causing neighbouring YSOs to appear as more evolved sources.
Plain text summary
This poster has 4 slides with black backgrounds, white borders and font unless otherwise stated.
Slide 1:
Title slide - a photo of NGC2264 inside its red natal nebula as the background. Cartoon hand holds magnifying glass over centre of NGC2264. Title positioned top central. Letters of “INDICATE” are sequential colours of the rainbow such that “I” is red and “E” is violet. This colour convention is used for the word INDICATE throughout the poster.
At the bottom (left to right): the logo for ICYBOB, University of Exeter, author name/affiliation, University of Leeds, SFM.
Slide 2:
Explains how INDICATE works. At the top, centrally placed is the title “What Is INDICATE?”.
Top 2/3 of slide has two paragraphs of text (left) and a figure (right). The first paragraph in orange font gives the short explanation that INDICATE assigns an index to each star in a cluster to quantify its degree of association. The higher the value of its index, the more spatially clustered a star is.
The index, I, is defined in the second paragraph and its equation given. A star’s index is the ratio of the number of neighbours within a distance, r, compared to the expected number from an evenly spaced distribution of the same density/parameter space as the cluster. Calibrated against random distributions, INDICATE can determine if a star is “Clustered” or “Dispersed”. Links to Buckner et al. (2019) and to download INDICATE are provided.
Figure shows two examples of the index being calculated, plotted on a white background with orange borders. There is 1 blue dot representing the target star in each plot in the centre of a red circle of radius ‘r’. Within this circle there are (left) 20 and (right) 3 black dots representing neighbour stars. The expected number of neighbours is 5 therefore (left) I=20/5=4 and (right) I=3/5=0.6.
Slide 3:
Shows our results for NGC2264. The left half of the slide is a NASA SST photo of NGC2264. Properties are listed in the top left corner:
1) Distance~720pc
2) Age~5Myr
3) O-type binary “SMon” in North
4) South younger & star formation active
On the right side is the title “Results with NGC2264”. A paragraph of text states the proportion of Young Stellar Objects (YSOs) clustered, and the degree of spatial concentration of these clustered objects, decreases with increasing evolutionary stage. Below are two visual representations of this statement:
1) Four pie charts show the percentage of objects identified as “Clustered” and “Dispersed” (one for each evolutionary stage). Percentage clustered decreases sequentially from 69.4% for least evolved (Class 0/I) to 7.7% for most evolved (Class III) objects.
2) Bar chart of evolutionary stage (X-axis) vs. “Clustered” objects typical index values (Y-axis). Shows sequential decrease in the index value from 5.2 (Class 0/I) to 2.8 (Class III).
Slide 4:
Compares these results with Gaia proper motion data. Motions of Class II and III objects are plotted on separate purple boarder figures over an orange Herschel 70μm map of NGC2264. Class II motions are consistent with the properties of known structure in south, but Class III motions are dispersed and randomised. Both have outward trajectory motions in older northern region. SMon is marked on the Class III plot with a ‘x’ and encompassed by two concentric circles representing 0.1deg and 0.05deg radius. Here, Class III’s show the spatial & kinematic behaviour of Class II’s.
Conclusions:
- dynamical evolution is responsible for present distributions
- prolonged sequential star formation has been occurring in cluster
- stellar feedback from SMon is causing neighbour YSOs to appear as more evolved sources
Links to Buckner et al. (2020) provided.
Slide 1:
Title slide - a photo of NGC2264 inside its red natal nebula as the background. Cartoon hand holds magnifying glass over centre of NGC2264. Title positioned top central. Letters of “INDICATE” are sequential colours of the rainbow such that “I” is red and “E” is violet. This colour convention is used for the word INDICATE throughout the poster.
At the bottom (left to right): the logo for ICYBOB, University of Exeter, author name/affiliation, University of Leeds, SFM.
Slide 2:
Explains how INDICATE works. At the top, centrally placed is the title “What Is INDICATE?”.
Top 2/3 of slide has two paragraphs of text (left) and a figure (right). The first paragraph in orange font gives the short explanation that INDICATE assigns an index to each star in a cluster to quantify its degree of association. The higher the value of its index, the more spatially clustered a star is.
The index, I, is defined in the second paragraph and its equation given. A star’s index is the ratio of the number of neighbours within a distance, r, compared to the expected number from an evenly spaced distribution of the same density/parameter space as the cluster. Calibrated against random distributions, INDICATE can determine if a star is “Clustered” or “Dispersed”. Links to Buckner et al. (2019) and to download INDICATE are provided.
Figure shows two examples of the index being calculated, plotted on a white background with orange borders. There is 1 blue dot representing the target star in each plot in the centre of a red circle of radius ‘r’. Within this circle there are (left) 20 and (right) 3 black dots representing neighbour stars. The expected number of neighbours is 5 therefore (left) I=20/5=4 and (right) I=3/5=0.6.
Slide 3:
Shows our results for NGC2264. The left half of the slide is a NASA SST photo of NGC2264. Properties are listed in the top left corner:
1) Distance~720pc
2) Age~5Myr
3) O-type binary “SMon” in North
4) South younger & star formation active
On the right side is the title “Results with NGC2264”. A paragraph of text states the proportion of Young Stellar Objects (YSOs) clustered, and the degree of spatial concentration of these clustered objects, decreases with increasing evolutionary stage. Below are two visual representations of this statement:
1) Four pie charts show the percentage of objects identified as “Clustered” and “Dispersed” (one for each evolutionary stage). Percentage clustered decreases sequentially from 69.4% for least evolved (Class 0/I) to 7.7% for most evolved (Class III) objects.
2) Bar chart of evolutionary stage (X-axis) vs. “Clustered” objects typical index values (Y-axis). Shows sequential decrease in the index value from 5.2 (Class 0/I) to 2.8 (Class III).
Slide 4:
Compares these results with Gaia proper motion data. Motions of Class II and III objects are plotted on separate purple boarder figures over an orange Herschel 70μm map of NGC2264. Class II motions are consistent with the properties of known structure in south, but Class III motions are dispersed and randomised. Both have outward trajectory motions in older northern region. SMon is marked on the Class III plot with a ‘x’ and encompassed by two concentric circles representing 0.1deg and 0.05deg radius. Here, Class III’s show the spatial & kinematic behaviour of Class II’s.
Conclusions:
- dynamical evolution is responsible for present distributions
- prolonged sequential star formation has been occurring in cluster
- stellar feedback from SMon is causing neighbour YSOs to appear as more evolved sources
Links to Buckner et al. (2020) provided.
Poster file
Poster Title
INDICATE: A novel tool to robustly study the star formation history of a cluster
Url
a.buckner@exeter.ac.uk