Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations

P. Santini, D. J. Rosario, L. Shao, D. Lutz, R. Maiolino, D. M. Alexander, B. Altieri, P. Andreani, H. Aussel, F. E. Bauer, S. Berta, A. Bongiovanni, W. N. Brandt, M. Brusa, J. Cepa, A. Cimatti, E. Daddi, D. Elbaz, A. Fontana, N. M. Förster SchreiberR. Genzel, A. Grazian, E. Le Floc'H, B. Magnelli, V. Mainieri, R. Nordon, A. M. Pérez Garcia, A. Poglitsch, P. Popesso, F. Pozzi, L. Riguccini, G. Rodighiero, M. Salvato, M. Sanchez-Portal, E. Sturm, L. J. Tacconi, I. Valtchanov, S. Wuyts

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Abstract

We compare the average star formation (SF) activity in X-ray selected AGN hosts with a mass-matched control sample of inactive galaxies, including both star forming and quiescent sources, in the 0.5 < z < 2.5 redshift range. Recent observations carried out by PACS, the 60-210 μm photometric camera on board the Herschel Space Observatory, in GOODS-S, GOODS-N and COSMOS allow us to obtain an unbiased estimate of the far-IR luminosity, and hence of the SF properties, of the two samples. Accurate AGN host stellar mass estimates are obtained by decomposing their total emission into the stellar and the nuclear components. We report evidence of a higher average SF activity in AGN hosts with respect to the control sample of inactive galaxies. The level of SF enhancement is modest (∼0.26 dex at ∼3σ confidence level) at low X-ray luminosities (L X ≈ 10 43.5 erg s -1) and more pronounced (0.56 dex at > 10σ confidence level) in the hosts of luminous AGNs. However, when comparing to star forming galaxies only, AGN hosts are found broadly consistent with the locus of their "main sequence". We investigate the relative far-IR luminosity distributions of active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly star forming systems among AGN hosts. Although different interpretations are possible, we explain our findings as a consequence of a twofold AGN growth path: faint AGNs evolve through secular processes, with instantaneous AGNaccretion not tightly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and star formation, possibly through major mergers. While an increased SF activity with respect to inactive galaxies of similar mass is expected in the latter, we interpret the modest SF offsets measured in low-L X AGN hosts as either a) generated by non-synchronous accretion and SF histories in a merger scenario or b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far-IR luminosity distributions favour the latter scenario.

Original languageEnglish (US)
Article numberA109
JournalAstronomy and Astrophysics
Volume540
DOIs
StatePublished - Apr 12 2012

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star formation rate
star formation
galaxies
merger
stars
accretion
luminosity
active galaxies
loci
rate
confidence
histories
history
x rays

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Santini, P., Rosario, D. J., Shao, L., Lutz, D., Maiolino, R., Alexander, D. M., ... Wuyts, S. (2012). Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations. Astronomy and Astrophysics, 540, [A109]. https://doi.org/10.1051/0004-6361/201118266
Santini, P. ; Rosario, D. J. ; Shao, L. ; Lutz, D. ; Maiolino, R. ; Alexander, D. M. ; Altieri, B. ; Andreani, P. ; Aussel, H. ; Bauer, F. E. ; Berta, S. ; Bongiovanni, A. ; Brandt, W. N. ; Brusa, M. ; Cepa, J. ; Cimatti, A. ; Daddi, E. ; Elbaz, D. ; Fontana, A. ; Förster Schreiber, N. M. ; Genzel, R. ; Grazian, A. ; Le Floc'H, E. ; Magnelli, B. ; Mainieri, V. ; Nordon, R. ; Pérez Garcia, A. M. ; Poglitsch, A. ; Popesso, P. ; Pozzi, F. ; Riguccini, L. ; Rodighiero, G. ; Salvato, M. ; Sanchez-Portal, M. ; Sturm, E. ; Tacconi, L. J. ; Valtchanov, I. ; Wuyts, S. / Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations. In: Astronomy and Astrophysics. 2012 ; Vol. 540.
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title = "Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations",
abstract = "We compare the average star formation (SF) activity in X-ray selected AGN hosts with a mass-matched control sample of inactive galaxies, including both star forming and quiescent sources, in the 0.5 < z < 2.5 redshift range. Recent observations carried out by PACS, the 60-210 μm photometric camera on board the Herschel Space Observatory, in GOODS-S, GOODS-N and COSMOS allow us to obtain an unbiased estimate of the far-IR luminosity, and hence of the SF properties, of the two samples. Accurate AGN host stellar mass estimates are obtained by decomposing their total emission into the stellar and the nuclear components. We report evidence of a higher average SF activity in AGN hosts with respect to the control sample of inactive galaxies. The level of SF enhancement is modest (∼0.26 dex at ∼3σ confidence level) at low X-ray luminosities (L X ≈ 10 43.5 erg s -1) and more pronounced (0.56 dex at > 10σ confidence level) in the hosts of luminous AGNs. However, when comparing to star forming galaxies only, AGN hosts are found broadly consistent with the locus of their {"}main sequence{"}. We investigate the relative far-IR luminosity distributions of active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly star forming systems among AGN hosts. Although different interpretations are possible, we explain our findings as a consequence of a twofold AGN growth path: faint AGNs evolve through secular processes, with instantaneous AGNaccretion not tightly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and star formation, possibly through major mergers. While an increased SF activity with respect to inactive galaxies of similar mass is expected in the latter, we interpret the modest SF offsets measured in low-L X AGN hosts as either a) generated by non-synchronous accretion and SF histories in a merger scenario or b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far-IR luminosity distributions favour the latter scenario.",
author = "P. Santini and Rosario, {D. J.} and L. Shao and D. Lutz and R. Maiolino and Alexander, {D. M.} and B. Altieri and P. Andreani and H. Aussel and Bauer, {F. E.} and S. Berta and A. Bongiovanni and Brandt, {W. N.} and M. Brusa and J. Cepa and A. Cimatti and E. Daddi and D. Elbaz and A. Fontana and {F{\"o}rster Schreiber}, {N. M.} and R. Genzel and A. Grazian and {Le Floc'H}, E. and B. Magnelli and V. Mainieri and R. Nordon and {P{\'e}rez Garcia}, {A. M.} and A. Poglitsch and P. Popesso and F. Pozzi and L. Riguccini and G. Rodighiero and M. Salvato and M. Sanchez-Portal and E. Sturm and Tacconi, {L. J.} and I. Valtchanov and S. Wuyts",
year = "2012",
month = "4",
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doi = "10.1051/0004-6361/201118266",
language = "English (US)",
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journal = "Astronomy and Astrophysics",
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Santini, P, Rosario, DJ, Shao, L, Lutz, D, Maiolino, R, Alexander, DM, Altieri, B, Andreani, P, Aussel, H, Bauer, FE, Berta, S, Bongiovanni, A, Brandt, WN, Brusa, M, Cepa, J, Cimatti, A, Daddi, E, Elbaz, D, Fontana, A, Förster Schreiber, NM, Genzel, R, Grazian, A, Le Floc'H, E, Magnelli, B, Mainieri, V, Nordon, R, Pérez Garcia, AM, Poglitsch, A, Popesso, P, Pozzi, F, Riguccini, L, Rodighiero, G, Salvato, M, Sanchez-Portal, M, Sturm, E, Tacconi, LJ, Valtchanov, I & Wuyts, S 2012, 'Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations', Astronomy and Astrophysics, vol. 540, A109. https://doi.org/10.1051/0004-6361/201118266

Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations. / Santini, P.; Rosario, D. J.; Shao, L.; Lutz, D.; Maiolino, R.; Alexander, D. M.; Altieri, B.; Andreani, P.; Aussel, H.; Bauer, F. E.; Berta, S.; Bongiovanni, A.; Brandt, W. N.; Brusa, M.; Cepa, J.; Cimatti, A.; Daddi, E.; Elbaz, D.; Fontana, A.; Förster Schreiber, N. M.; Genzel, R.; Grazian, A.; Le Floc'H, E.; Magnelli, B.; Mainieri, V.; Nordon, R.; Pérez Garcia, A. M.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Salvato, M.; Sanchez-Portal, M.; Sturm, E.; Tacconi, L. J.; Valtchanov, I.; Wuyts, S.

In: Astronomy and Astrophysics, Vol. 540, A109, 12.04.2012.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations

AU - Santini, P.

AU - Rosario, D. J.

AU - Shao, L.

AU - Lutz, D.

AU - Maiolino, R.

AU - Alexander, D. M.

AU - Altieri, B.

AU - Andreani, P.

AU - Aussel, H.

AU - Bauer, F. E.

AU - Berta, S.

AU - Bongiovanni, A.

AU - Brandt, W. N.

AU - Brusa, M.

AU - Cepa, J.

AU - Cimatti, A.

AU - Daddi, E.

AU - Elbaz, D.

AU - Fontana, A.

AU - Förster Schreiber, N. M.

AU - Genzel, R.

AU - Grazian, A.

AU - Le Floc'H, E.

AU - Magnelli, B.

AU - Mainieri, V.

AU - Nordon, R.

AU - Pérez Garcia, A. M.

AU - Poglitsch, A.

AU - Popesso, P.

AU - Pozzi, F.

AU - Riguccini, L.

AU - Rodighiero, G.

AU - Salvato, M.

AU - Sanchez-Portal, M.

AU - Sturm, E.

AU - Tacconi, L. J.

AU - Valtchanov, I.

AU - Wuyts, S.

PY - 2012/4/12

Y1 - 2012/4/12

N2 - We compare the average star formation (SF) activity in X-ray selected AGN hosts with a mass-matched control sample of inactive galaxies, including both star forming and quiescent sources, in the 0.5 < z < 2.5 redshift range. Recent observations carried out by PACS, the 60-210 μm photometric camera on board the Herschel Space Observatory, in GOODS-S, GOODS-N and COSMOS allow us to obtain an unbiased estimate of the far-IR luminosity, and hence of the SF properties, of the two samples. Accurate AGN host stellar mass estimates are obtained by decomposing their total emission into the stellar and the nuclear components. We report evidence of a higher average SF activity in AGN hosts with respect to the control sample of inactive galaxies. The level of SF enhancement is modest (∼0.26 dex at ∼3σ confidence level) at low X-ray luminosities (L X ≈ 10 43.5 erg s -1) and more pronounced (0.56 dex at > 10σ confidence level) in the hosts of luminous AGNs. However, when comparing to star forming galaxies only, AGN hosts are found broadly consistent with the locus of their "main sequence". We investigate the relative far-IR luminosity distributions of active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly star forming systems among AGN hosts. Although different interpretations are possible, we explain our findings as a consequence of a twofold AGN growth path: faint AGNs evolve through secular processes, with instantaneous AGNaccretion not tightly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and star formation, possibly through major mergers. While an increased SF activity with respect to inactive galaxies of similar mass is expected in the latter, we interpret the modest SF offsets measured in low-L X AGN hosts as either a) generated by non-synchronous accretion and SF histories in a merger scenario or b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far-IR luminosity distributions favour the latter scenario.

AB - We compare the average star formation (SF) activity in X-ray selected AGN hosts with a mass-matched control sample of inactive galaxies, including both star forming and quiescent sources, in the 0.5 < z < 2.5 redshift range. Recent observations carried out by PACS, the 60-210 μm photometric camera on board the Herschel Space Observatory, in GOODS-S, GOODS-N and COSMOS allow us to obtain an unbiased estimate of the far-IR luminosity, and hence of the SF properties, of the two samples. Accurate AGN host stellar mass estimates are obtained by decomposing their total emission into the stellar and the nuclear components. We report evidence of a higher average SF activity in AGN hosts with respect to the control sample of inactive galaxies. The level of SF enhancement is modest (∼0.26 dex at ∼3σ confidence level) at low X-ray luminosities (L X ≈ 10 43.5 erg s -1) and more pronounced (0.56 dex at > 10σ confidence level) in the hosts of luminous AGNs. However, when comparing to star forming galaxies only, AGN hosts are found broadly consistent with the locus of their "main sequence". We investigate the relative far-IR luminosity distributions of active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly star forming systems among AGN hosts. Although different interpretations are possible, we explain our findings as a consequence of a twofold AGN growth path: faint AGNs evolve through secular processes, with instantaneous AGNaccretion not tightly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and star formation, possibly through major mergers. While an increased SF activity with respect to inactive galaxies of similar mass is expected in the latter, we interpret the modest SF offsets measured in low-L X AGN hosts as either a) generated by non-synchronous accretion and SF histories in a merger scenario or b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far-IR luminosity distributions favour the latter scenario.

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