| 1. |
- Agertz, Oscar, et al.
(författare)
-
Vintergatan - i. The origins of chemically, kinematically, and structurally distinct discs in a simulated milky way-mass galaxy
- 2021
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:4, s. 5826-5845
-
Tidskriftsartikel (refereegranskat)abstract
- Spectroscopic surveys of the Milky Way's stars have revealed spatial, chemical, and kinematical structures that encode its history. In this work, we study their origins using a cosmological zoom simulation, VINTERGATAN, of a MilkyWay-mass disc galaxy. We find that in connection to the last major merger at z ∼ 1.5, cosmological accretion leads to the rapid formation of an outer, metal-poor, low-[α/Fe] gas disc around the inner, metal-rich galaxy containing the old high-[α/Fe] stars. This event leads to a bimodality in [α/Fe] over a range of [Fe/H]. A detailed analysis of how the galaxy evolves since z ∼ 1 is presented. We demonstrate the way in which inside-out growth shapes the radial surface density and metallicity profile and how radial migration preferentially relocates stars from the inner disc to the outer disc. Secular disc heating is found to give rise to increasing velocity dispersions and scale heights with stellar age, which together with disc flaring explains several trends observed in the MilkyWay, including shallower radial [Fe/H] profiles above the mid-plane.We show how the galaxy formation scenario imprints non-trivial mappings between structural associations (i.e. thick and thin discs), velocity dispersions, α-enhancements, and ages of stars; e.g. the most metal-poor stars in the low-[α/Fe] sequence are found to have a scale height comparable to old high-[α/Fe] stars. Finally, we illustrate how at low spatial resolution, comparable to the thickness of the galaxy, the proposed pathway to distinct sequences in [α/Fe]-[Fe/H] cannot be captured.
|
|
| 2. |
- Andersson, Eric P., et al.
(författare)
-
INFERNO : Galactic winds in dwarf galaxies with star-by-star simulations including runaway stars
- 2023
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 521:2, s. 2196-2214
-
Tidskriftsartikel (refereegranskat)abstract
- The formation and evolution of galaxies have proved sensitive to the inclusion of stellar feedback, which is therefore crucial to any successful galaxy model. We present INFERNO, a new model for hydrodynamic simulations of galaxies, which incorporates resolved stellar objects with star-by-star calculations of when and where the injection of enriched material, momentum, and energy takes place. INFERNO treats early stellar kinematics to include phenomena such as walkaway and runaway stars. We employ this innovative model on simulations of a dwarf galaxy and demonstrate that our physically motivated stellar feedback model can drive vigorous galactic winds. This is quantified by mass and metal loading factors in the range of 10–100, and an energy loading factor close to unity. Outflows are established close to the disc, are highly multiphase, spanning almost 8 orders of magnitude in temperature, and with a clear dichotomy between mass ejected in cold, slow-moving (T ≲ 5 × 104 K, v < 100 km s-1) gas and energy ejected in hot, fast-moving (T > 106 K, v > 100 km s-1) gas. In contrast to massive disc galaxies, we find a surprisingly weak impact of the early stellar kinematics, with runaway stars having little to no effect on our results, despite exploding in diffuse gas outside the dense star-forming gas, as well as outside the galactic disc entirely. We demonstrate that this weak impact in dwarf galaxies stems from a combination of strong feedback and a porous interstellar medium, which obscure any unique signatures that runaway stars provide.
|
|
| 3. |
- Andersson, Eric P., et al.
(författare)
-
Pre-supernova feedback sets the star cluster mass function to a power law and reduces the cluster formation efficiency
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361. ; 681
-
Tidskriftsartikel (refereegranskat)abstract
- Context. The star cluster initial mass function is observed to have an inverse power law exponent around 2, yet there is no consensus on what determines this distribution, and why some variation is observed in different galaxies. Furthermore, the cluster formation efficiency (CFE) covers a range of values, particularly when considering different environments. These clusters are often used to empirically constrain star formation and as fundamental units for stellar feedback models. Detailed galaxy models must therefore accurately capture the basic properties of observed clusters to be considered predictive. Aims. We study how feedback mechanisms acting on different timescales and with different energy budgets affect the star cluster mass function and CFE. Methods. We use hydrodynamical simulations of a dwarf galaxy as a laboratory to study star cluster formation. We test different combinations of stellar feedback mechanisms, including stellar winds, ionizing radiation, and supernovae (SNe). Results. Each feedback mechanism affects the CFE and cluster mass function. Increasing the feedback budget by combining the different types of feedback decreases the CFE by reducing the number of massive clusters. Ionizing radiation is found to be especially influential. This effect depends on the timing of feedback initiation, as shown by comparing early and late feedback. Early feedback occurs from ionizing radiation and stellar winds with onset immediately after a massive star is formed. Late feedback occurs when energy injection only starts after the main-sequence lifetime of the most massive SN progenitor, a timing that is further influenced by the choice of the most massive SN progenitor. Late feedback alone results in a broad, flat mass function, approaching a log-normal shape in the complete absence of feedback. Early feedback, on the other hand, produces a power-law cluster mass function with lower CFE, albeit with a steeper slope than that usually observed.
|
|
| 4. |
- Andersson, Eric P., et al.
(författare)
-
Runaway stars masquerading as star formation in galactic outskirts
- 2021
-
Ingår i: Monthly Notices of the Royal Astronomical Society: Letters. - : Oxford University Press (OUP). - 1745-3925 .- 1745-3933. ; 502:1, s. 29-34
-
Tidskriftsartikel (refereegranskat)abstract
- In the outskirts of nearby spiral galaxies, star formation is observed in extremely low gas surface densities. Star formation in these regions, where the interstellar medium is dominated by diffuse atomic hydrogen, is difficult to explain with classic star formation theories. In this letter, we introduce runaway stars as an explanation for this observation. Runaway stars, produced by collisional dynamics in young stellar clusters, can travel kiloparsecs during their main-sequence lifetime. Using galactic-scale hydrodynamic simulations including a treatment of individual stars, we demonstrate that this mechanism enables the ejection of young massive stars into environments where the gas is not dense enough to trigger star formation. This results in the appearance of star formation in regions where it ought to be impossible. We conclude that runaway stars are a contributing, if not dominant, factor to the observations of star formation in the outskirts of spiral galaxies.
|
|
| 5. |
- Andersson Granberg, Tobias, 1973-, et al.
(författare)
-
Sensor Requirements for Logistics Analysis of Emergency Incident Sites
- 2020
-
Ingår i: Proceedings of the 17th ISCRAM Conference. - : Information Systems for Crisis Response and Management. - 9781949373271 ; , s. 952-960
-
Konferensbidrag (refereegranskat)abstract
- Using sensors to collect data at emergency incident sites can facilitate analysis of the logistic operations. This can be used to improve planning and preparedness for new operations. Furthermore, real-time information from the sensors can serve as operational decision support. In this work in progress, we investigate the requirements on the sensors, and on the sensor data, to facilitate such an analysis. Through observations of exercises, the potential of using sensors for data collection is explored, and the requirements are considered. The results show that the potential benefits are significant, especially for tracking patients, and understanding the interaction between the response actors. However, the sensors need to be quite advanced in order to capture the necessary data.
|
|
| 6. |
- Andersson, M., et al.
(författare)
-
Evaluation of response in patients with hepatocellular carcinoma treated with intratumoral dendritic cell vaccination using intravoxel incoherent motion (IVIM) MRI and histogram analysis
- 2023
-
Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 64:1, s. 32-41
-
Tidskriftsartikel (refereegranskat)abstract
- Background Immunotherapy of hepatocellular carcinoma (HCC) is an emerging method with promising results. Immunotherapy can have an antitumor effect without affecting tumor size, calling for functional imaging methods for response evaluation. Purpose To evaluate the response to intratumoral injections with the immune primer ilixadencel in HCCs with diffusion-weighted magnetic resonance imaging (DW-MRI) using intravoxel incoherent motion (IVIM) and histogram analysis. Material and Methods A total of 17 patients with advanced HCC were treated with intratumoral injections with ilixadencel on three occasions 2-5 weeks apart. The patients were examined with IVIM before each injection as well as approximately three months after the first injection. Results The 10th percentile of perfusion-related parameter D* decreased significantly after the first and second intratumoral injections of ilixadencel compared to baseline (P < 0.05). There was a non-significant trend of lower median region of interest f (perfusion fraction) before injection 2 compared to baseline (P = 0.07). There were significant correlations between the 10th percentile and median of D at baseline and change in tumor size after three months (r = 0.79, P < 0.01 and r = 0.72, P < 0.05, respectively). Conclusion DW-MRI with IVIM and histogram analysis revealed significant reductions of D* early after treatment as well as an association between D at baseline and smaller tumor growth at three months. The lower percentiles (10th and 50th) were found more important. Further research is needed to confirm our preliminary findings of reduced perfusion after ilixadencel vaccinations, suggesting a treatment effect on HCC.
|
|
| 7. |
- Andersson, Oscar, 1968-
(författare)
-
Italiensk-amerikaner i Bostons North End : En omanalys av William Foote Whytes fältanteckningar
- 2022. - 1
-
Bok (refereegranskat)abstract
- I sin nya bok gör Oscar Andersson en omanalys av William Foote Whytes fältanteckningar från hans klassiska fältstudie Street Corner Society från 1943, som utspelar sig i Bostons stadsdel North End under andra hälften av 1930-talet. Att få tillgång till en annan antropologs kompletta samling fältanteckningar är unikt. Antropologer ser fältanteckningar som sin intellektuella egendom och det finns ingen utomstående som kan kräva att få se dem. Forskning har visat att antropologer oroar sig över att fältanteckningarna – vid en jämförande analys – inte validerar etnografin, vilket gör att de ogärna lämnar ut dem. Bill Whyte var tvärtom en tillitsfull person som såg det som en självklarhet att efterkommande forskargenerationer skulle få tillgång till hans ocensurerade fältanteckningar. Whytes oredigerade fältanteckningar och banbrytande observationsmetoder analyseras ingående i denna studie av Oscar Andersson. Bill Whytes fältanteckningar har använts analytiskt för att historiskt beskriva och teoretiskt förklara italiensk-amerikaners kultur i Bostons North End i teman som både överlappar och skiljer sig från Whytes. Dessa teman binds samman av rumsliga och temporala grupphändelser, och innefattar den stora depressionen under 1930-talet, emigrationen från Italien till USA, stadsdelen North Ends befolkningsutveckling, lokalpolitik, organiserad brottslighet, arbetsmarknadskonflikter, social rörlighet och gruppkonflikter som kunde blossa upp i det gäng av cornerboys, som Bill Whyte umgicks med i North End. En händelse som också ingående återberättas är mobiliseringen av invånarna för att protestera mot stadsdelens sanitära och hygieniska missförhållanden som befolkningen tvingades leva under.
|
|
| 8. |
- Andersson, Oscar, 1968-
(författare)
-
The Moral System of Corner boys and College boys in Boston’s North End During the Great Depression of the 1930s : A Reinterpretation of William Foote Whyte’s Street Corner Society Based on His Fieldnotes and an Unpublished Case Study
- 2021
-
Ingår i: Journal of the North End Historical Society. - Boston : North End Historical Society. - 9780578831329 ; , s. 23-49
-
Bokkapitel (refereegranskat)abstract
- The article is about the attitudes of corner boys and college boys’ to social mobility, showing that the 1930s was a watershed era. The first generation of Italians were often farmers and fishermen who became industrial workers in the United States. The second generation of Italians had adapted to American cultural conditions to varying degrees, with commitments in both the local community and the majority society. Corner boys planned for a future in the local community. College boys strove to pursue a career outside the social and geographical boundaries of the community. Corner boys learned the rules of society on the street. College boys were handpicked at school and in the settlement house to become middle-class Americans. Corner boys regarded college boys as hypocrites who put their short-term interests before those of the local community. The schisms between corner boys and college boys were an indication that the family values of the local Italian community were changing. But it was not until some time after the Second World War that the third and fourth generations of Italians had acquired moral values similar to those of the average American about abortion, mixed marriages, homosexuality, sexual abstinence before marriage, and divorce.
|
|
| 9. |
|
|
| 10. |
|
|
