V. Könyves - Academia.edu (original) (raw)

Papers by V. Könyves

Astronomische Nachrichten, 2013

ABSTRACT We present a molecular line emission study of the LDN1188 dark cloud complex located in ... more ABSTRACT We present a molecular line emission study of the LDN1188 dark cloud complex located in Cepheus. In this work we focused on the densest parts of the cloud and on the close neighbourhood of infrared point sources. We made ammonia mapping with the Effelsberg 100-m radio telescope and identified 3 dense cores. CS(1--0), CS(2--1) and HCO$^{+}$(1--0) measurements performed with the Onsala 20\,m telescope revealed the distribution of dense molecular material. The molecular line measurements were supplemented by mapping the dust emission at 1.2\,mm in some selected directions using the IRAM 30\,m telescope. With these data we could work out a likely evolutionary sequence in this dark clould complex.

ABSTRACT The Herschel Space Observatory provides a unique opportunity to improve our global under... more ABSTRACT The Herschel Space Observatory provides a unique opportunity to improve our global understanding of the earliest phases of star formation. I will present an overview of the first results from the Gould Belt survey, one of the largest key projects with Herschel. The immediate objective of this imaging survey of nearby clouds is to obtain complete samples of prestellar cores and Class 0 protostars with well characterized luminosities, temperatures, and density profiles, as well as robust core mass functions in a variety of environments. The main scientific goal is to elucidate the physical mechanisms responsible for the formation of prestellar cores out of the diffuse interstellar medium. Our early findings confirm the existence of a close relationship between the prestellar core mass function (CMF) and the stellar initial mass function (IMF). The Herschel images also reveal a rich network of filaments in every interstellar cloud and suggest an intimate connection between the filamentary structure of the ISM and the formation process of prestellar cores. Remarkably, filaments are omnipresent even in unbound, non-star-forming complexes and seem to be characterized by a narrow distribution of widths around ˜ 0.1 pc. This characteristic width approximately corresponds to the sonic scale below which interstellar turbulence becomes subsonic in diffuse gas, supporting the view that the filaments may form as a result of the dissipation of large-scale turbulence. In active star-forming regions, most of the prestellar cores identified with Herschel are located within gravitationally unstable filaments above a critical threshold ˜ 15 M_⊙/pc in mass per unit length or ˜ 150 M_⊙/pc^2 in gas surface density. Altogether, the Herschel results favor a scenario in which interstellar filaments and prestellar cores represent two fundamental steps in the star formation process: First, large-scale magneto-hydrodynamic turbulence generates a complex web of filaments in the ISM; second, the densest filaments fragment and develop prestellar cores (and ultimately protostars) via gravitational instability.

Monthly Notices of the Royal Astronomical Society, 2014

ABSTRACT The density and temperature structures of dense cores in the L1495 cloud of the Taurus s... more ABSTRACT The density and temperature structures of dense cores in the L1495 cloud of the Taurus star-forming region are investigated using Herschel SPIRE and PACS images in the 70 mu\mumum, 160 mu\mumum, 250 mu\mumum, 350 mu\mumum and 500 mu\mumum continuum bands. A sample consisting of 20 cores, selected using spectral and spatial criteria, is analysed using a new maximum likelihood technique, COREFIT, which takes full account of the instrumental point spread functions. We obtain central dust temperatures, T_0T_0T0, in the range 6-12 K and find that, in the majority of cases, the radial density falloff at large radial distances is consistent with the r−2r^{-2}r−2 variation expected for Bonnor-Ebert spheres. Two of our cores exhibit a significantly steeper falloff, however, and since both appear to be gravitationally unstable, such behaviour may have implications for collapse models. We find a strong negative correlation between T0T_0T_0 and peak column density, as expected if the dust is heated predominantly by the interstellar radiation field. At the temperatures we estimate for the core centres, carbon-bearing molecules freeze out as ice mantles on dust grains, and this behaviour is supported here by the lack of correspondence between our estimated core locations and the previously-published positions of H$^{13}$CO$^+$ peaks. On this basis, our observations suggest a sublimation-zone radius typically sim104\sim 10^4sim104 AU. Comparison with previously-published N$_2$H$^+$ data at 8400 AU resolution, however, shows no evidence for N$_2$H$^+$ depletion at that resolution.

Astronomy & Astrophysics, 2013

Astronomy & Astrophysics, 2011

Abstract: The filament IRDC G035. 39--00.33 in the W48 molecular complex is one of the darkest in... more Abstract: The filament IRDC G035. 39--00.33 in the W48 molecular complex is one of the darkest infrared clouds observed by\ textit {Spitzer}. It has been observed by the PACS (70 and 160\, micron\ micron micron) and SPIRE (250, 350, and 500\, micron\ micron micron) cameras of the\ textit { ...

Astronomy & Astrophysics, 2013

ABSTRACT We investigate the gas velocity dispersions of a sample of filaments recently detected a... more ABSTRACT We investigate the gas velocity dispersions of a sample of filaments recently detected as part of the Herschel Gould Belt Survey in the IC 5146, Aquila, and Polaris interstellar clouds. To measure these velocity dispersions, we use 13CO, C18O, and N2H+ line observations obtained with the IRAM 30 m telescope. Correlating our velocity dispersion measurements with the filament column densities derived from Herschel data, we show that interstellar filaments can be divided into two regimes: thermally subcritical filaments, which have transonic velocity dispersions (cs ≲ σtot < 2 cs) independent of column density and are gravitationally unbound; and thermally supercritical filaments, which have higher velocity dispersions scaling roughly as the square root of column density (σtot ∝ Σ00.5) and which are self-gravitating. The higher velocity dispersions of supercritical filaments may not directly arise from supersonic interstellar turbulence but may be driven by gravitational contraction/accretion. Based on our observational results, we propose an evolutionary scenario whereby supercritical filaments undergo gravitational contraction and increase in mass per unit length through accretion of background material, while remaining in rough virial balance. We further suggest that this accretion process allows supercritical filaments to keep their approximately constant inner widths (~0.1 pc) while contracting. Based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Appendix A available in electronic form at http://www.aanda.org

Astronomy and Astrophysics, 2010

V. Könyves1, Ph. André1, A. Men'shchikov1, N. Schneider1, D.... more V. Könyves1, Ph. André1, A. Men'shchikov1, N. Schneider1, D. Arzoumanian1, S. Bontemps1,2,3, M. Attard1, F. Motte1, P. Didelon1, A. Maury4, and A. Abergel5, B. Ali6, J.-P. Baluteau7, J.-Ph. Bernard8, L. Cambrésy9, P. Cox10, J. Di Francesco11, AM di ...

Astronomy and Astrophysics, 2010

D. Ward-Thompson1, JM Kirk1, P. André2, P. Saraceno3, P. Didelon2, V. Könyves2, N. Schneider2, A.... more D. Ward-Thompson1, JM Kirk1, P. André2, P. Saraceno3, P. Didelon2, V. Könyves2, N. Schneider2, A. Abergel4, J.-P. Baluteau5, J.-Ph. Bernard6, S. Bontemps2, L. Cambrésy7, P. Cox8, J. Di Francesco9, AM Di Giorgio3, M. Griffin1, P. Hargrave1, M. Huang10, JZ Li10, ...

Astronomy & Astrophysics, 2012

We present APEX/P-ArTéMiS 450 µm continuum observations of RCW 36 and the adjacent ridge, a high-... more We present APEX/P-ArTéMiS 450 µm continuum observations of RCW 36 and the adjacent ridge, a high-mass high-column density filamentary structure at the centre of the Vela C molecular cloud. These observations, at higher resolution than Herschel's SPIRE camera, reveal clear fragmentation of the central star-forming ridge. Combined with PACS far-infrared and SPIRE sub-millimetre observations from the Herschel HOBYS project we build a high resolution column density map of the region mapped with P-ArTéMiS. We extract the radial density profile of the Vela C ridge which with a ∼ 0.1 pc central width is consistent with that measured for low-mass star-forming filaments in the Herschel Gould Belt survey. Direct comparison with Serpens South, of the Gould Belt Aquila complex, reveals many similarities between the two regions. Despite likely different formation mechanisms and histories, the Vela C ridge and Serpens South filament share common characteristics, including their filament central widths.

Monthly Notices of the Royal Astronomical Society, 2014

We present the results of Herschel HOBYS photometric mapping combined with BIMA observations and ... more We present the results of Herschel HOBYS photometric mapping combined with BIMA observations and additional archival data, and perform an in-depth study of the evolutionary phases of the star-forming clumps in W 48A and their surroundings. Age estimates for the compact sources were derived from bolometric luminosities and envelope masses, which were obtained from the dust continuum emission, and agree within an order of magnitude with age estimates from molecular line and radio data. The clumps in W 48A are linearly aligned by age (east-old to west-young): we find a UC Hii region, a young stellar object (YSO) with class II methanol maser emission, a YSO with a massive outflow, and finally the NH 2 D prestellar cores from Pillai et al. This remarkable positioning reflects the (star) formation history of the region. We find that it is unlikely that the star formation in the W 48A molecular cloud was triggered by the UC Hii region and discuss the Aquila supershell expansion as a mayor influence on the evolution of W 48A. We conclude that the combination of Herschel continuum data with interferometric molecular line and radio continuum data is important to derive trustworthy age estimates and interpret the origin of large scale structures through kinematic information.

Astronomische Nachrichten, 2013

ABSTRACT We present a molecular line emission study of the LDN1188 dark cloud complex located in ... more ABSTRACT We present a molecular line emission study of the LDN1188 dark cloud complex located in Cepheus. In this work we focused on the densest parts of the cloud and on the close neighbourhood of infrared point sources. We made ammonia mapping with the Effelsberg 100-m radio telescope and identified 3 dense cores. CS(1--0), CS(2--1) and HCO$^{+}$(1--0) measurements performed with the Onsala 20\,m telescope revealed the distribution of dense molecular material. The molecular line measurements were supplemented by mapping the dust emission at 1.2\,mm in some selected directions using the IRAM 30\,m telescope. With these data we could work out a likely evolutionary sequence in this dark clould complex.

ABSTRACT The Herschel Space Observatory provides a unique opportunity to improve our global under... more ABSTRACT The Herschel Space Observatory provides a unique opportunity to improve our global understanding of the earliest phases of star formation. I will present an overview of the first results from the Gould Belt survey, one of the largest key projects with Herschel. The immediate objective of this imaging survey of nearby clouds is to obtain complete samples of prestellar cores and Class 0 protostars with well characterized luminosities, temperatures, and density profiles, as well as robust core mass functions in a variety of environments. The main scientific goal is to elucidate the physical mechanisms responsible for the formation of prestellar cores out of the diffuse interstellar medium. Our early findings confirm the existence of a close relationship between the prestellar core mass function (CMF) and the stellar initial mass function (IMF). The Herschel images also reveal a rich network of filaments in every interstellar cloud and suggest an intimate connection between the filamentary structure of the ISM and the formation process of prestellar cores. Remarkably, filaments are omnipresent even in unbound, non-star-forming complexes and seem to be characterized by a narrow distribution of widths around ˜ 0.1 pc. This characteristic width approximately corresponds to the sonic scale below which interstellar turbulence becomes subsonic in diffuse gas, supporting the view that the filaments may form as a result of the dissipation of large-scale turbulence. In active star-forming regions, most of the prestellar cores identified with Herschel are located within gravitationally unstable filaments above a critical threshold ˜ 15 M_⊙/pc in mass per unit length or ˜ 150 M_⊙/pc^2 in gas surface density. Altogether, the Herschel results favor a scenario in which interstellar filaments and prestellar cores represent two fundamental steps in the star formation process: First, large-scale magneto-hydrodynamic turbulence generates a complex web of filaments in the ISM; second, the densest filaments fragment and develop prestellar cores (and ultimately protostars) via gravitational instability.

Monthly Notices of the Royal Astronomical Society, 2014

ABSTRACT The density and temperature structures of dense cores in the L1495 cloud of the Taurus s... more ABSTRACT The density and temperature structures of dense cores in the L1495 cloud of the Taurus star-forming region are investigated using Herschel SPIRE and PACS images in the 70 mu\mumum, 160 mu\mumum, 250 mu\mumum, 350 mu\mumum and 500 mu\mumum continuum bands. A sample consisting of 20 cores, selected using spectral and spatial criteria, is analysed using a new maximum likelihood technique, COREFIT, which takes full account of the instrumental point spread functions. We obtain central dust temperatures, T_0T_0T0, in the range 6-12 K and find that, in the majority of cases, the radial density falloff at large radial distances is consistent with the r−2r^{-2}r−2 variation expected for Bonnor-Ebert spheres. Two of our cores exhibit a significantly steeper falloff, however, and since both appear to be gravitationally unstable, such behaviour may have implications for collapse models. We find a strong negative correlation between T0T_0T_0 and peak column density, as expected if the dust is heated predominantly by the interstellar radiation field. At the temperatures we estimate for the core centres, carbon-bearing molecules freeze out as ice mantles on dust grains, and this behaviour is supported here by the lack of correspondence between our estimated core locations and the previously-published positions of H$^{13}$CO$^+$ peaks. On this basis, our observations suggest a sublimation-zone radius typically sim104\sim 10^4sim104 AU. Comparison with previously-published N$_2$H$^+$ data at 8400 AU resolution, however, shows no evidence for N$_2$H$^+$ depletion at that resolution.

Astronomy & Astrophysics, 2013

Astronomy & Astrophysics, 2011

Abstract: The filament IRDC G035. 39--00.33 in the W48 molecular complex is one of the darkest in... more Abstract: The filament IRDC G035. 39--00.33 in the W48 molecular complex is one of the darkest infrared clouds observed by\ textit {Spitzer}. It has been observed by the PACS (70 and 160\, micron\ micron micron) and SPIRE (250, 350, and 500\, micron\ micron micron) cameras of the\ textit { ...

Astronomy & Astrophysics, 2013

ABSTRACT We investigate the gas velocity dispersions of a sample of filaments recently detected a... more ABSTRACT We investigate the gas velocity dispersions of a sample of filaments recently detected as part of the Herschel Gould Belt Survey in the IC 5146, Aquila, and Polaris interstellar clouds. To measure these velocity dispersions, we use 13CO, C18O, and N2H+ line observations obtained with the IRAM 30 m telescope. Correlating our velocity dispersion measurements with the filament column densities derived from Herschel data, we show that interstellar filaments can be divided into two regimes: thermally subcritical filaments, which have transonic velocity dispersions (cs ≲ σtot < 2 cs) independent of column density and are gravitationally unbound; and thermally supercritical filaments, which have higher velocity dispersions scaling roughly as the square root of column density (σtot ∝ Σ00.5) and which are self-gravitating. The higher velocity dispersions of supercritical filaments may not directly arise from supersonic interstellar turbulence but may be driven by gravitational contraction/accretion. Based on our observational results, we propose an evolutionary scenario whereby supercritical filaments undergo gravitational contraction and increase in mass per unit length through accretion of background material, while remaining in rough virial balance. We further suggest that this accretion process allows supercritical filaments to keep their approximately constant inner widths (~0.1 pc) while contracting. Based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Appendix A available in electronic form at http://www.aanda.org

Astronomy and Astrophysics, 2010

V. Könyves1, Ph. André1, A. Men'shchikov1, N. Schneider1, D.... more V. Könyves1, Ph. André1, A. Men'shchikov1, N. Schneider1, D. Arzoumanian1, S. Bontemps1,2,3, M. Attard1, F. Motte1, P. Didelon1, A. Maury4, and A. Abergel5, B. Ali6, J.-P. Baluteau7, J.-Ph. Bernard8, L. Cambrésy9, P. Cox10, J. Di Francesco11, AM di ...

Astronomy and Astrophysics, 2010

D. Ward-Thompson1, JM Kirk1, P. André2, P. Saraceno3, P. Didelon2, V. Könyves2, N. Schneider2, A.... more D. Ward-Thompson1, JM Kirk1, P. André2, P. Saraceno3, P. Didelon2, V. Könyves2, N. Schneider2, A. Abergel4, J.-P. Baluteau5, J.-Ph. Bernard6, S. Bontemps2, L. Cambrésy7, P. Cox8, J. Di Francesco9, AM Di Giorgio3, M. Griffin1, P. Hargrave1, M. Huang10, JZ Li10, ...

Astronomy & Astrophysics, 2012

We present APEX/P-ArTéMiS 450 µm continuum observations of RCW 36 and the adjacent ridge, a high-... more We present APEX/P-ArTéMiS 450 µm continuum observations of RCW 36 and the adjacent ridge, a high-mass high-column density filamentary structure at the centre of the Vela C molecular cloud. These observations, at higher resolution than Herschel's SPIRE camera, reveal clear fragmentation of the central star-forming ridge. Combined with PACS far-infrared and SPIRE sub-millimetre observations from the Herschel HOBYS project we build a high resolution column density map of the region mapped with P-ArTéMiS. We extract the radial density profile of the Vela C ridge which with a ∼ 0.1 pc central width is consistent with that measured for low-mass star-forming filaments in the Herschel Gould Belt survey. Direct comparison with Serpens South, of the Gould Belt Aquila complex, reveals many similarities between the two regions. Despite likely different formation mechanisms and histories, the Vela C ridge and Serpens South filament share common characteristics, including their filament central widths.

Monthly Notices of the Royal Astronomical Society, 2014

We present the results of Herschel HOBYS photometric mapping combined with BIMA observations and ... more We present the results of Herschel HOBYS photometric mapping combined with BIMA observations and additional archival data, and perform an in-depth study of the evolutionary phases of the star-forming clumps in W 48A and their surroundings. Age estimates for the compact sources were derived from bolometric luminosities and envelope masses, which were obtained from the dust continuum emission, and agree within an order of magnitude with age estimates from molecular line and radio data. The clumps in W 48A are linearly aligned by age (east-old to west-young): we find a UC Hii region, a young stellar object (YSO) with class II methanol maser emission, a YSO with a massive outflow, and finally the NH 2 D prestellar cores from Pillai et al. This remarkable positioning reflects the (star) formation history of the region. We find that it is unlikely that the star formation in the W 48A molecular cloud was triggered by the UC Hii region and discuss the Aquila supershell expansion as a mayor influence on the evolution of W 48A. We conclude that the combination of Herschel continuum data with interferometric molecular line and radio continuum data is important to derive trustworthy age estimates and interpret the origin of large scale structures through kinematic information.