| 1. |
- Marconi, A., et al.
(författare)
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ANDES, the high resolution spectrograph for the ELT : science case, baseline design and path to construction
- 2022
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Ingår i: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY IX. - : SPIE - International Society for Optical Engineering. - 9781510653504 - 9781510653498
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Konferensbidrag (refereegranskat)abstract
- The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of similar to 100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 mu m with the goal of extending it to 0.35-2.4 mu m with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coude room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.
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| 2. |
- Sabbi, E., et al.
(författare)
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The Resolved Stellar Populations in the LEGUS Galaxies
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 235:1
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Tidskriftsartikel (refereegranskat)abstract
- The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14 Me, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems.
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| 3. |
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| 4. |
- Zackrisson, E., et al.
(författare)
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Do blue compact galaxies have red halos?
- 2009
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Red halos are faint, extended and extremely red structures that have been reported around various types of galaxies since the mid-1990s. The colours of these halos are too red to be reconciled with any hitherto known type of stellar population, and instead indicative of a very bottom-heavy stellar initial mass function (IMF). Due to the large mass-to-light ratios of such stellar halos, they could contribute substantially to the baryonic masses of galaxies while adding very little to their overall luminosities. The red halos of galaxies therefore constitute potential reservoirs for some of the baryons still missing from inventories in the low-redshift Universe. While most studies of red halos have focused on disk galaxies, a red excess has also been reported in the faint outskirts of blue compact galaxies (BCGs). A bottom-heavy IMF can explain the colours of these structures as well, but due to model degeneracies, stellar populations with standard IMFs and abnormally high metallicities have also been demonstrated to fit the data. Here, we show that due to recent developments in the field of spectral synthesis, the metallicities required in this alternative scenario may be less extreme than previously thought. This suggests that the red excess seen in the outskirts of BCGs may stem from a normal, intermediate-metallicity host galaxy rather than a red halo of the type seen around disk galaxies. The inferred host metallicity does, however, still require the host to be more metal-rich than the gas in the central starburst of BCGs, in contradiction with current simulations of how BCGs form.
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| 5. |
- Bergvall, Nils, et al.
(författare)
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Emission line flux limits in four QSO metal line absorbers
- 1997
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 321:3, s. 771-775
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to detect the early phases of star formation in massive galaxies, we have searched for Ly alpha and [O II]lambda 3727 emission from four QSO metal absorption line systems and possible associated galaxies, using narrow-band filters. None of th
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| 6. |
- Bergvall, N, et al.
(författare)
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LWS spectroscopy of the luminous blue compact galaxy Haro 11
- 2000
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER-VERLAG. - 0004-6361. ; 359:1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of far infrared (FIR) spectroscopy of the luminous blue compact galaxy (BCG) Hare 11 (ESO 350-IG38) obtained with the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO) in low resolution mode. This metal poor
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| 7. |
- Bergvall, N, et al.
(författare)
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Optical/near-IR surface photometry of blue low surface brightness galaxies
- 1999
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 341:3, s. 697-708
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Tidskriftsartikel (refereegranskat)abstract
- We present luminosity profiles, colour profiles and disk parameters based on near-infrared JHK surface photometry of a sample of blue low surface brightness galaxies (BLSBGs). The results are discussed along with previously obtained optical data. We find
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| 8. |
- Bergvall, N, et al.
(författare)
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Starburst dwarfs - Fueling and morphological evolution
- 1999
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Ingår i: ASTROPHYSICS AND SPACE SCIENCE. - : KLUWER ACADEMIC PUBL. - 0004-640X. ; 269, s. 625-628
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Tidskriftsartikel (refereegranskat)abstract
- The effects of mergers in low mass galaxies are poorly understood. In this paper we analyze different observational evidences which support the view that mergers can trigger starbursts in dwarf galaxies. We discuss the relationships between blue compact g
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| 9. |
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| 10. |
- Dahlen, Tomas, et al.
(författare)
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The Stockholm Vimos Supernova Survey (SVISS) - First Results From An Intermediate Redshift Sn Survey
- 2009
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Konferensbidrag (refereegranskat)abstract
- The aim of the Stockholm VIMOS Supernova Survey is to find and characterize supernovae in the redshift range 0.1 to 1.2 and to derive accurate supernova rate densities for this redshift range. A preliminary analysis show that we have 14 prime SN candidates and an additional 23 less secure detections in one of our search fields. A sample of R+I light curves for the prime candidates will be presented. We will also show some results from testing of our supernova search pipeline and our supernova typing method.
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