BL Lacertae (Lac) objects that are detected at very high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the strength of the intergalactic magnetic field. Unfortunately, since most blazars have featureless optical spectra that preclude a redshift determination, a substantial fraction of these VHE extragalactic sources cannot be used for cosmological studies. To assess whether molecular lines are a viable way to establish distances, we have undertaken a pilot programme at the Institut of Millimétrique (IRAM) 30m telescope to search for CO lines in three BL Lac objects with known redshifts. We report a positive detection of MH2~3×108 M ⊙ towards 1ES 1959+650, but due to the poor quality of the baseline, this value is affected by a large systematic uncertainty. For the remaining two sources, W Comae and RGB J0710+591, we derive 3σ upper limits at, respectively, MH2<8.0×108 and 1.6 × 10 9 M ⊙, assuming a line width of 150kms -1 and a standard conversion factor α = 4 M ⊙ (Kkms -1pc 2) -1. If these low molecular gas masses are typical for blazars, blind redshift searches in molecular lines are currently unfeasible. However, deep observations are still a promising way to obtain precise redshifts for sources whose approximate distances are known via indirect methods. Our observations further reveal a deficiency of molecular gas in BL Lac objects compared to quasars, suggesting that the host galaxies of these two types of active galactic nuclei (AGN) are not drawn from the same parent population. Future observations are needed to assess whether this discrepancy is statistically significant, but our pilot programme shows how studies of the interstellar medium in AGN can provide key information to explore the connection between the active nuclei and the host galaxies. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Fumagalli, M., Dessauges-Zavadsky, M., Furniss, A., Prochaska, J., Williams, D., Kaplan, K., et al. (2012). A search of CO emission lines in blazars: The low molecular gas content of BL Lac objects compared to quasars. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 424(3), 2276-2283 [10.1111/j.1365-2966.2012.21391.x].

A search of CO emission lines in blazars: The low molecular gas content of BL Lac objects compared to quasars

Fumagalli M.;
2012

Abstract

BL Lacertae (Lac) objects that are detected at very high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the strength of the intergalactic magnetic field. Unfortunately, since most blazars have featureless optical spectra that preclude a redshift determination, a substantial fraction of these VHE extragalactic sources cannot be used for cosmological studies. To assess whether molecular lines are a viable way to establish distances, we have undertaken a pilot programme at the Institut of Millimétrique (IRAM) 30m telescope to search for CO lines in three BL Lac objects with known redshifts. We report a positive detection of MH2~3×108 M ⊙ towards 1ES 1959+650, but due to the poor quality of the baseline, this value is affected by a large systematic uncertainty. For the remaining two sources, W Comae and RGB J0710+591, we derive 3σ upper limits at, respectively, MH2<8.0×108 and 1.6 × 10 9 M ⊙, assuming a line width of 150kms -1 and a standard conversion factor α = 4 M ⊙ (Kkms -1pc 2) -1. If these low molecular gas masses are typical for blazars, blind redshift searches in molecular lines are currently unfeasible. However, deep observations are still a promising way to obtain precise redshifts for sources whose approximate distances are known via indirect methods. Our observations further reveal a deficiency of molecular gas in BL Lac objects compared to quasars, suggesting that the host galaxies of these two types of active galactic nuclei (AGN) are not drawn from the same parent population. Future observations are needed to assess whether this discrepancy is statistically significant, but our pilot programme shows how studies of the interstellar medium in AGN can provide key information to explore the connection between the active nuclei and the host galaxies. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.
Si
Articolo in rivista - Articolo scientifico
Scientifica
BL Lacertae objects: general; BL Lacertae objects: individual: 1ES 1959+650; Galaxies: active; Galaxies: distances and redshifts; Galaxies: ISM; ISM: molecules
English
2276
2283
8
Fumagalli, M., Dessauges-Zavadsky, M., Furniss, A., Prochaska, J., Williams, D., Kaplan, K., et al. (2012). A search of CO emission lines in blazars: The low molecular gas content of BL Lac objects compared to quasars. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 424(3), 2276-2283 [10.1111/j.1365-2966.2012.21391.x].
Fumagalli, M; Dessauges-Zavadsky, M; Furniss, A; Prochaska, J; Williams, D; Kaplan, K; Hogan, M
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/280695
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