CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Young Star Clusters and Clumps in the Local Universe: The effect of galactic environment on star formation
Stockholm University, Faculty of Science, Department of Astronomy.ORCID iD: 0000-0003-1427-2456
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Stars do not form in isolation, but rather out of a hierarchical structure set by the turbulence of the interstellar medium. At the densest peak of the gas distribution, the star formation process can produce young star clusters (YSCs), which are gravitationally bound systems of stars with mass between ~100 and 106 MSun and typical size of few parsecs. At larger scales, clusters are themselves arranged into cluster complexes, on scales of hundreds of parsecs and up to kiloparsec scales, which are usually referred to as ‘star-forming clumps’.

Observations of local star-forming galaxies show that YSCs form over a wide range of galactic environment. However, it is not yet clear if and how the galactic environment relates to the properties of star clusters. I present the results obtained by studying the YSC population of the nearby spiral galaxy M51. We find that the cluster mass function, dN/dM, can be described by a power-law with a -2 slope and an exponential truncation at 105 MSun, consistent with what is observed in similar galaxies in the literature. The shape of the mass function is similar when looking at increasing galactocentric distances. We observe significant differences, however, when comparing clusters located in the spiral arm with those the inter-arm environments. On average, more massive clusters are formed in the spiral arms, as also previously found for the YSC progenitors, the giant molecular clouds (GMCs). Finally, we see that clusters are more quickly disrupted in denser environments, as expected if their disruption is mainly caused by tidal interaction with dense gas structures like the GMCs.

I have also undertaken the analysis of the interplay between galactic scale properties and larger star forming units, the stellar clumps. The analysis has been conducted in a sample of 14 low-redshift starburst galaxies, the Lyman-Alpha Reference Sample (LARS). The elevated star formation rate densities of such galaxies allow to form clumps with densities comparable to clumps at high-redshift, typically more massive and denser than what is normally observed in the local universe. The clumps in the LARS galaxies contribute to a large fraction to the UV flux of the galaxy itself (in many galaxies > 50%), resulting in galaxies which appear ‘clumpy’. In agreement with formation theories we observe that clumpiness is higher in galaxies with higher SFR surface density and dominated by turbulent gas motion.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University , 2019. , p. 91
Keywords [en]
Galaxies, Star formation, Star clusters
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-163079ISBN: 978-91-7797-554-0 (print)ISBN: 978-91-7797-555-7 (electronic)OAI: oai:DiVA.org:su-163079DiVA, id: diva2:1271532
Public defence
2019-02-15, sal FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2019-01-23 Created: 2018-12-17 Last updated: 2019-01-22Bibliographically approved
List of papers
1. The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution
Open this publication in new window or tab >>The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution
Show others...
2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 1, p. 996-1018Article in journal (Refereed) Published
Abstract [en]

Recently acquired WFC3 UV (F275W and F336W) imaging mosaics under the Legacy Extragalactic UV Survey (LEGUS), combined with archival ACS data of M51, are used to study the young star cluster (YSC) population of this interacting system. Our newly extracted source catalogue contains 2834 cluster candidates, morphologically classified to be compact and uniform in colour, for which ages, masses and extinction are derived. In this first work we study the main properties of the YSC population of the whole galaxy, considering a mass-limited sample. Both luminosity and mass functions follow a power-law shape with slope -2, but at high luminosities and masses a dearth of sources is observed. The analysis of the mass function suggests that it is best fitted by a Schechter function with slope -2 and a truncation mass at 1.00 +/- 0.12 x 10(5) M-circle dot . Through Monte Carlo simulations, we confirm this result and link the shape of the luminosity function to the presence of a truncation in the mass function. A mass limited age function analysis, between 10 and 200 Myr, suggests that the cluster population is undergoing only moderate disruption. We observe little variation in the shape of the mass function at masses above 1 x 10(4) M-circle dot over this age range. The fraction of star formation happening in the form of bound clusters in M51 is similar to 20 per cent in the age range 10-100 Myr and little variation is observed over the whole range from 1 to 200 Myr.

Keywords
galaxies: individual: M51, NGC 5194, galaxies: star clusters: general, galaxies: star formation
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-150036 (URN)10.1093/mnras/stx2403 (DOI)000415653600079 ()
Available from: 2017-12-18 Created: 2017-12-18 Last updated: 2018-12-19Bibliographically approved
2. The young star cluster population of M51 with LEGUS - II. Testing environmental dependences
Open this publication in new window or tab >>The young star cluster population of M51 with LEGUS - II. Testing environmental dependences
Show others...
2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, no 2, p. 1670-1694Article in journal (Refereed) Published
Abstract [en]

It has recently been established that the properties of young star clusters (YSCs) can vary as a function of the galactic environment in which they are found. We use the cluster catalogue produced by the Legacy ExtragalacticUVSurvey (LEGUS) collaboration to investigate cluster properties in the spiral galaxy M51. We analyse the cluster population as a function of galactocentric distance and in arm and inter-arm regions. The cluster mass function exhibits a similar shape at all radial bins, described by a power law with a slope close to -2 and an exponential truncation around 10(5) M-circle dot. While the mass functions of the YSCs in the spiral arm and inter-arm regions have similar truncation masses, the inter-arm region mass function has a significantly steeper slope than the one in the arm region, a trend that is also observed in the giant molecular cloud mass function and predicted by simulations. The age distribution of clusters is dependent on the region considered, and is consistent with rapid disruption only in dense regions, while little disruption is observed at large galactocentric distances and in the inter-arm region. The fraction of stars forming in clusters does not show radial variations, despite the drop in the H-2 surface density measured as a function of galactocentric distance. We suggest that the higher disruption rate observed in the inner part of the galaxy is likely at the origin of the observed flat cluster formation efficiency radial profile.

Keywords
galaxies: individual: M51, galaxies: individual: NGC 5194, galaxies: star clusters: general, galaxies: star formation
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-157771 (URN)10.1093/mnras/sty577 (DOI)000434663200015 ()
Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2018-12-19Bibliographically approved
3. Star-forming clumps in the Lyman Alpha Reference Sample of galaxies - I. Photometric analysis and clumpiness
Open this publication in new window or tab >>Star-forming clumps in the Lyman Alpha Reference Sample of galaxies - I. Photometric analysis and clumpiness
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-163078 (URN)
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-01-22Bibliographically approved
4. Star-forming clumps in the Lyman Alpha Reference Sample of galaxies - II. Ages and ionization budge
Open this publication in new window or tab >>Star-forming clumps in the Lyman Alpha Reference Sample of galaxies - II. Ages and ionization budge
(English)Manuscript (preprint) (Other academic)
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-163153 (URN)
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-01-22Bibliographically approved

Open Access in DiVA

Young Star Clusters and Clumps in the Local Universe(8023 kB)28 downloads
File information
File name FULLTEXT01.pdfFile size 8023 kBChecksum SHA-512
40a05a82f2e7161fb098f5cfbc11498f8aa6e39c4f7a13b243e999278236ef09e0cb8690b66e60864f6b0b2224eedf743f4f685a67c554a86f5f62b5dc64d4b8
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Messa, Matteo
By organisation
Department of Astronomy
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
Total: 28 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 343 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf