An ISOPHOT study of the disk of galaxy NGC 6946: 60 μm infrared and radio continuum correlation

N. Y. Lu, G. Helou, R. Tuffs, C. Xu, S. Malhotra, M. W. Werner, H. Thronson

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We use the ISOPHOT 60 μm image of Tuffs et al. (1996) to study the 60/μm light distribution and its correlation with radio continuum within the disk of spiral galaxy NGC 6946, and to resolve the long-standing IRAS controversy as to whether the infrared-to-radio continuum ratio, Q, decreases radially out in galaxy disks. Our main results are: (1) The disk at 60 μm also appears to follow an exponential fall-off. Its e-folding scale-length lies between 1′.3 and an upper limit of 1′.9, obtained from the mean radial profile between 1′.5 and 4′ in radius. This scale length is smaller than that derived from the radio continuum data at either 20 cm or 6 cm, with or without the thermal component removed, at a significance level of ≳ 2σ. (2) From 1′.5 to 4′ in radius, the 60/μm-to-radio continuum surface brightness ratio, Q, decreases by a factor of 1.5 to 1.7 on average. These quantitative results agree with that of Marsh & Helou (1995) using IRAS HiRes data, but not with that of Fitt et al. (1992) based on IRAS CPC data. Our results also fit into the picture of the radio disk as a "smeared" version of the infrared disk, but are not consistent with the picture in which the variation of Q is a result of the thermal and non-thermal radio components having two distinct, constant values of the infrared-to-radio ratio.

Original languageEnglish (US)
JournalAstronomy and Astrophysics
Volume315
Issue number2
StatePublished - Nov 10 1996
Externally publishedYes

Fingerprint

Infrared Astronomy Satellite
radio
galaxies
continuums
marshlands
radii
disk galaxies
spiral galaxies
folding
brightness
profiles
marsh

Keywords

  • Galaxies: individual/NGC 6946
  • Galaxies: ISM
  • Infrared: galaxies
  • Radio continuum: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Lu, N. Y., Helou, G., Tuffs, R., Xu, C., Malhotra, S., Werner, M. W., & Thronson, H. (1996). An ISOPHOT study of the disk of galaxy NGC 6946: 60 μm infrared and radio continuum correlation. Astronomy and Astrophysics, 315(2).

An ISOPHOT study of the disk of galaxy NGC 6946 : 60 μm infrared and radio continuum correlation. / Lu, N. Y.; Helou, G.; Tuffs, R.; Xu, C.; Malhotra, S.; Werner, M. W.; Thronson, H.

In: Astronomy and Astrophysics, Vol. 315, No. 2, 10.11.1996.

Research output: Contribution to journalArticle

Lu, NY, Helou, G, Tuffs, R, Xu, C, Malhotra, S, Werner, MW & Thronson, H 1996, 'An ISOPHOT study of the disk of galaxy NGC 6946: 60 μm infrared and radio continuum correlation', Astronomy and Astrophysics, vol. 315, no. 2.
Lu NY, Helou G, Tuffs R, Xu C, Malhotra S, Werner MW et al. An ISOPHOT study of the disk of galaxy NGC 6946: 60 μm infrared and radio continuum correlation. Astronomy and Astrophysics. 1996 Nov 10;315(2).
Lu, N. Y. ; Helou, G. ; Tuffs, R. ; Xu, C. ; Malhotra, S. ; Werner, M. W. ; Thronson, H. / An ISOPHOT study of the disk of galaxy NGC 6946 : 60 μm infrared and radio continuum correlation. In: Astronomy and Astrophysics. 1996 ; Vol. 315, No. 2.
@article{51e0639fab8641cd9c2305d420ecd9ca,
title = "An ISOPHOT study of the disk of galaxy NGC 6946: 60 μm infrared and radio continuum correlation",
abstract = "We use the ISOPHOT 60 μm image of Tuffs et al. (1996) to study the 60/μm light distribution and its correlation with radio continuum within the disk of spiral galaxy NGC 6946, and to resolve the long-standing IRAS controversy as to whether the infrared-to-radio continuum ratio, Q, decreases radially out in galaxy disks. Our main results are: (1) The disk at 60 μm also appears to follow an exponential fall-off. Its e-folding scale-length lies between 1′.3 and an upper limit of 1′.9, obtained from the mean radial profile between 1′.5 and 4′ in radius. This scale length is smaller than that derived from the radio continuum data at either 20 cm or 6 cm, with or without the thermal component removed, at a significance level of ≳ 2σ. (2) From 1′.5 to 4′ in radius, the 60/μm-to-radio continuum surface brightness ratio, Q, decreases by a factor of 1.5 to 1.7 on average. These quantitative results agree with that of Marsh & Helou (1995) using IRAS HiRes data, but not with that of Fitt et al. (1992) based on IRAS CPC data. Our results also fit into the picture of the radio disk as a {"}smeared{"} version of the infrared disk, but are not consistent with the picture in which the variation of Q is a result of the thermal and non-thermal radio components having two distinct, constant values of the infrared-to-radio ratio.",
keywords = "Galaxies: individual/NGC 6946, Galaxies: ISM, Infrared: galaxies, Radio continuum: galaxies",
author = "Lu, {N. Y.} and G. Helou and R. Tuffs and C. Xu and S. Malhotra and Werner, {M. W.} and H. Thronson",
year = "1996",
month = "11",
day = "10",
language = "English (US)",
volume = "315",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "2",

}

TY - JOUR

T1 - An ISOPHOT study of the disk of galaxy NGC 6946

T2 - 60 μm infrared and radio continuum correlation

AU - Lu, N. Y.

AU - Helou, G.

AU - Tuffs, R.

AU - Xu, C.

AU - Malhotra, S.

AU - Werner, M. W.

AU - Thronson, H.

PY - 1996/11/10

Y1 - 1996/11/10

N2 - We use the ISOPHOT 60 μm image of Tuffs et al. (1996) to study the 60/μm light distribution and its correlation with radio continuum within the disk of spiral galaxy NGC 6946, and to resolve the long-standing IRAS controversy as to whether the infrared-to-radio continuum ratio, Q, decreases radially out in galaxy disks. Our main results are: (1) The disk at 60 μm also appears to follow an exponential fall-off. Its e-folding scale-length lies between 1′.3 and an upper limit of 1′.9, obtained from the mean radial profile between 1′.5 and 4′ in radius. This scale length is smaller than that derived from the radio continuum data at either 20 cm or 6 cm, with or without the thermal component removed, at a significance level of ≳ 2σ. (2) From 1′.5 to 4′ in radius, the 60/μm-to-radio continuum surface brightness ratio, Q, decreases by a factor of 1.5 to 1.7 on average. These quantitative results agree with that of Marsh & Helou (1995) using IRAS HiRes data, but not with that of Fitt et al. (1992) based on IRAS CPC data. Our results also fit into the picture of the radio disk as a "smeared" version of the infrared disk, but are not consistent with the picture in which the variation of Q is a result of the thermal and non-thermal radio components having two distinct, constant values of the infrared-to-radio ratio.

AB - We use the ISOPHOT 60 μm image of Tuffs et al. (1996) to study the 60/μm light distribution and its correlation with radio continuum within the disk of spiral galaxy NGC 6946, and to resolve the long-standing IRAS controversy as to whether the infrared-to-radio continuum ratio, Q, decreases radially out in galaxy disks. Our main results are: (1) The disk at 60 μm also appears to follow an exponential fall-off. Its e-folding scale-length lies between 1′.3 and an upper limit of 1′.9, obtained from the mean radial profile between 1′.5 and 4′ in radius. This scale length is smaller than that derived from the radio continuum data at either 20 cm or 6 cm, with or without the thermal component removed, at a significance level of ≳ 2σ. (2) From 1′.5 to 4′ in radius, the 60/μm-to-radio continuum surface brightness ratio, Q, decreases by a factor of 1.5 to 1.7 on average. These quantitative results agree with that of Marsh & Helou (1995) using IRAS HiRes data, but not with that of Fitt et al. (1992) based on IRAS CPC data. Our results also fit into the picture of the radio disk as a "smeared" version of the infrared disk, but are not consistent with the picture in which the variation of Q is a result of the thermal and non-thermal radio components having two distinct, constant values of the infrared-to-radio ratio.

KW - Galaxies: individual/NGC 6946

KW - Galaxies: ISM

KW - Infrared: galaxies

KW - Radio continuum: galaxies

UR - http://www.scopus.com/inward/record.url?scp=0009497816&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0009497816&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0009497816

VL - 315

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 2

ER -