J/ApJS/174/337 Star formation in nuclear rings (Mazzuca+, 2008)
A connection between star formation in nuclear rings and their host galaxies.
Mazzuca L.M., Knapen J.H., Veilleux S., Regan M.W.
<Astrophys. J. Suppl. Ser., 174, 337-365 (2008)>
=2008ApJS..174..337M 2008ApJS..174..337M
ADC_Keywords: Galaxies, ring ; Equivalent widths ; H II regions ;
Photometry, H-alpha
Keywords: galaxies: spiral - galaxies: structure - stars: formation
Abstract:
We present results from a photometric Hα survey of 22 nuclear
rings, aiming to provide insight into their star formation properties,
including age distribution, dynamical timescales, star formation
rates, and galactic bar influence. We find a clear relationship
between the position angles and ellipticities of the rings and those
of their host galaxies, which indicates the rings are in the same
plane as the disk and circular. We use population synthesis models to
estimate ages of each Hα-emitting (HII) region, which range from
1 to 10Myr throughout the rings. We find that approximately half of
the rings contain azimuthal age gradients that encompass at least 25%
of the ring, although there is no apparent relationship between the
presence or absence of age gradients and the morphology of the rings
or their host galaxies. NGC 1343, NGC 1530, and NGC 4321 show clear
bipolar age gradients, where the youngest HII regions are located near
the two contact points of the bar and ring. We speculate in these
cases that the gradients are related to an increased mass inflow rate
and/or an overall higher gas density in the ring, which would allow
for massive star formation to occur on short timescales, after which
the galactic rotation would transport the HII regions around the ring
as they age. Two-thirds of the barred galaxies show correlation
between the locations of the youngest HII region(s) in the ring and
the location of the contact points, which is consistent with
predictions from numerical modeling.
Description:
The ring images presented here are part of a larger William Herschel
Telescope (WHT) imaging survey (1999 and 2000) conducted to
characterize the nuclear and circumnuclear morphology in nearby
galaxies (Paper I, Knapen et al., 2006A&A...448..489K 2006A&A...448..489K).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
galaxies.dat 142 20 Galaxy list
tables.dat 37 399 NGC or IC HII regions detected associated with
the ring (tables 4 to 23 of the paper)
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See also:
J/AJ/128/2170 : Hα imaging of irregular galaxies (Hunter+, 2004)
Byte-by-byte Description of file: galaxies.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- NGC/IC Galaxy name
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 20 F4.1 s RAs Right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination sign (J2000)
26- 27 I2 arcmin DEm Declination sign (J2000)
29- 30 I2 arcsec DEs Declination sign (J2000)
34- 35 I2 --- NHII Number of HII regions in the galaxy
37-142 A106 --- Remarks Notes on the HII reguions detected.
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Byte-by-byte Description of file: tables.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- NGC/IC Galaxy name
10- 11 I2 --- [MKV2008] HII region number (1)
13- 17 F5.2 10-16W/m2 Flux Integrated flux (in 10-13erg/cm2/s)
19- 24 F6.2 10+32W Lum Luminosity (in 1037erg/s)
26- 30 I5 0.1nm EW Hα equivalent width (Å)
32- 35 F4.2 [0.1nm] logEW Logarithm of EW
37 I1 --- CorFlux [0/1] Flux correction (2)
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Note (1):
Since SExtractor detects all HII regions in the supplied image, extraneous HII
regions as well as the nucleus were included in the identification process.
These superfluous detections are not included in the tables but are instead
noted in the captions (above) for completeness sake.
Note (2): Flag as follows:
0 = In the cases where the I-band flux generated from SExtractor was not
modified;
1 = I-band flux needed to be modified in order to compensate for unrealistic
values (i.e., negative flux values or marginally positive flux values.
See section 4.2.1).
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Nomenclature note:
HII Region are <[MKV2008] NGC NNNN NN> or <[MKV2008] IC 1438 NN> in Simbad.
History:
From electronic version of the journal
References:
Knapen et al. Paper I. 2006A&A...448..489K 2006A&A...448..489K
(End) Emmanuelle Perret [CDS] 01-Oct-2009