ANOMALOUS MICROWAVE EMISSION in H II REGIONS: Is IT REALLY ANOMALOUS? the CASE of RCW 49

Roberta Paladini, Adriano Ingallinera, Claudia Agliozzo, Christopher T. Tibbs, Alberto Noriega-Crespo, Grazia Umana, Clive Dickinson, Corrado Trigilio

Resultado de la investigación: Article

4 Citas (Scopus)

Resumen

The detection of an excess of emission at microwave frequencies with respect to the predicted free-free emission has been reported for several Galactic H ii regions. Here, we investigate the case of RCW 49, for which the Cosmic Background Imager tentatively (∼3σ) detected Anomalous Microwave Emission (AME) at 31 GHz on angular scales of 7′. Using the Australia Telescope Compact Array, we carried out a multi-frequency (5, 19, and 34 GHz) continuum study of the region, complemented by observations of the H109α radio recombination line. The analysis shows that: (1) the spatial correlation between the microwave and IR emission persists on angular scales from 3.′4 to 0.″4, although the degree of the correlation slightly decreases at higher frequencies and on smaller angular scales; (2) the spectral indices between 1.4 and 5 GHz are globally in agreement with optically thin free-free emission, however, ∼30% of these are positive and much greater than -0.1, consistent with a stellar wind scenario; and (3) no major evidence for inverted free-free radiation is found, indicating that this is likely not the cause of the Anomalous Emission in RCW 49. Although our results cannot rule out the spinning dust hypothesis to explain the tentative detection of AME in RCW 49, they emphasize the complexity of astronomical sources that are very well known and studied, such as H ii regions, and suggest that, at least in these objects, the reported excess of emission might be ascribed to alternative mechanisms such as stellar winds and shocks.

Idioma originalEnglish
Número de artículo24
PublicaciónAstrophysical Journal
Volumen813
N.º1
DOI
EstadoPublished - 1 nov 2015

Huella dactilar

microwave emission
stellar winds
microwave frequencies
metal spinning
dust
shock
telescopes
recombination
continuums
causes
radiation
radio
microwave
detection

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Paladini, R., Ingallinera, A., Agliozzo, C., Tibbs, C. T., Noriega-Crespo, A., Umana, G., ... Trigilio, C. (2015). ANOMALOUS MICROWAVE EMISSION in H II REGIONS: Is IT REALLY ANOMALOUS? the CASE of RCW 49. Astrophysical Journal, 813(1), [24]. https://doi.org/10.1088/0004-637X/813/1/24
Paladini, Roberta ; Ingallinera, Adriano ; Agliozzo, Claudia ; Tibbs, Christopher T. ; Noriega-Crespo, Alberto ; Umana, Grazia ; Dickinson, Clive ; Trigilio, Corrado. / ANOMALOUS MICROWAVE EMISSION in H II REGIONS : Is IT REALLY ANOMALOUS? the CASE of RCW 49. En: Astrophysical Journal. 2015 ; Vol. 813, N.º 1.
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abstract = "The detection of an excess of emission at microwave frequencies with respect to the predicted free-free emission has been reported for several Galactic H ii regions. Here, we investigate the case of RCW 49, for which the Cosmic Background Imager tentatively (∼3σ) detected Anomalous Microwave Emission (AME) at 31 GHz on angular scales of 7′. Using the Australia Telescope Compact Array, we carried out a multi-frequency (5, 19, and 34 GHz) continuum study of the region, complemented by observations of the H109α radio recombination line. The analysis shows that: (1) the spatial correlation between the microwave and IR emission persists on angular scales from 3.′4 to 0.″4, although the degree of the correlation slightly decreases at higher frequencies and on smaller angular scales; (2) the spectral indices between 1.4 and 5 GHz are globally in agreement with optically thin free-free emission, however, ∼30{\%} of these are positive and much greater than -0.1, consistent with a stellar wind scenario; and (3) no major evidence for inverted free-free radiation is found, indicating that this is likely not the cause of the Anomalous Emission in RCW 49. Although our results cannot rule out the spinning dust hypothesis to explain the tentative detection of AME in RCW 49, they emphasize the complexity of astronomical sources that are very well known and studied, such as H ii regions, and suggest that, at least in these objects, the reported excess of emission might be ascribed to alternative mechanisms such as stellar winds and shocks.",
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Paladini, R, Ingallinera, A, Agliozzo, C, Tibbs, CT, Noriega-Crespo, A, Umana, G, Dickinson, C & Trigilio, C 2015, 'ANOMALOUS MICROWAVE EMISSION in H II REGIONS: Is IT REALLY ANOMALOUS? the CASE of RCW 49', Astrophysical Journal, vol. 813, n.º 1, 24. https://doi.org/10.1088/0004-637X/813/1/24

ANOMALOUS MICROWAVE EMISSION in H II REGIONS : Is IT REALLY ANOMALOUS? the CASE of RCW 49. / Paladini, Roberta; Ingallinera, Adriano; Agliozzo, Claudia; Tibbs, Christopher T.; Noriega-Crespo, Alberto; Umana, Grazia; Dickinson, Clive; Trigilio, Corrado.

En: Astrophysical Journal, Vol. 813, N.º 1, 24, 01.11.2015.

Resultado de la investigación: Article

TY - JOUR

T1 - ANOMALOUS MICROWAVE EMISSION in H II REGIONS

T2 - Is IT REALLY ANOMALOUS? the CASE of RCW 49

AU - Paladini, Roberta

AU - Ingallinera, Adriano

AU - Agliozzo, Claudia

AU - Tibbs, Christopher T.

AU - Noriega-Crespo, Alberto

AU - Umana, Grazia

AU - Dickinson, Clive

AU - Trigilio, Corrado

PY - 2015/11/1

Y1 - 2015/11/1

N2 - The detection of an excess of emission at microwave frequencies with respect to the predicted free-free emission has been reported for several Galactic H ii regions. Here, we investigate the case of RCW 49, for which the Cosmic Background Imager tentatively (∼3σ) detected Anomalous Microwave Emission (AME) at 31 GHz on angular scales of 7′. Using the Australia Telescope Compact Array, we carried out a multi-frequency (5, 19, and 34 GHz) continuum study of the region, complemented by observations of the H109α radio recombination line. The analysis shows that: (1) the spatial correlation between the microwave and IR emission persists on angular scales from 3.′4 to 0.″4, although the degree of the correlation slightly decreases at higher frequencies and on smaller angular scales; (2) the spectral indices between 1.4 and 5 GHz are globally in agreement with optically thin free-free emission, however, ∼30% of these are positive and much greater than -0.1, consistent with a stellar wind scenario; and (3) no major evidence for inverted free-free radiation is found, indicating that this is likely not the cause of the Anomalous Emission in RCW 49. Although our results cannot rule out the spinning dust hypothesis to explain the tentative detection of AME in RCW 49, they emphasize the complexity of astronomical sources that are very well known and studied, such as H ii regions, and suggest that, at least in these objects, the reported excess of emission might be ascribed to alternative mechanisms such as stellar winds and shocks.

AB - The detection of an excess of emission at microwave frequencies with respect to the predicted free-free emission has been reported for several Galactic H ii regions. Here, we investigate the case of RCW 49, for which the Cosmic Background Imager tentatively (∼3σ) detected Anomalous Microwave Emission (AME) at 31 GHz on angular scales of 7′. Using the Australia Telescope Compact Array, we carried out a multi-frequency (5, 19, and 34 GHz) continuum study of the region, complemented by observations of the H109α radio recombination line. The analysis shows that: (1) the spatial correlation between the microwave and IR emission persists on angular scales from 3.′4 to 0.″4, although the degree of the correlation slightly decreases at higher frequencies and on smaller angular scales; (2) the spectral indices between 1.4 and 5 GHz are globally in agreement with optically thin free-free emission, however, ∼30% of these are positive and much greater than -0.1, consistent with a stellar wind scenario; and (3) no major evidence for inverted free-free radiation is found, indicating that this is likely not the cause of the Anomalous Emission in RCW 49. Although our results cannot rule out the spinning dust hypothesis to explain the tentative detection of AME in RCW 49, they emphasize the complexity of astronomical sources that are very well known and studied, such as H ii regions, and suggest that, at least in these objects, the reported excess of emission might be ascribed to alternative mechanisms such as stellar winds and shocks.

KW - dust, extinction

KW - H II regions

KW - radio continuum: ISM

KW - radio lines: ISM

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Paladini R, Ingallinera A, Agliozzo C, Tibbs CT, Noriega-Crespo A, Umana G y otros. ANOMALOUS MICROWAVE EMISSION in H II REGIONS: Is IT REALLY ANOMALOUS? the CASE of RCW 49. Astrophysical Journal. 2015 nov 1;813(1). 24. https://doi.org/10.1088/0004-637X/813/1/24