J/ApJS/245/14 8um cores in the spiral arms of nearby galaxies (Elmegreen+, 2019)
Highly embedded 8um cores of star formation in the spiral arms and
filaments of 15 nearby disk galaxies.
Elmegreen B.G., Elmegreen D.M.
<Astrophys. J. Suppl. Ser., 245, 14 (2019)>
=2019ApJS..245...14E 2019ApJS..245...14E
ADC_Keywords: Galaxies, nearby; Photometry, infrared; Colors;
Interstellar medium
Keywords: Star formation; Star forming regions; Galaxy structure; Spiral arms;
Interstellar medium; Interstellar absorption; Interstellar clouds;
Interstellar filaments; Protostars
Abstract:
Spitzer Space Telescope observations of 15 spiral galaxies show
numerous dense cores at 8µm that are revealed primarily in unsharp
mask images. The cores are generally invisible in optical bands
because of extinction, and they are also indistinct at 8µm alone
because of contamination by more widespread diffuse emission. Several
hundred core positions, magnitudes, and colors from the four InfraRed
Array Camera bands are measured and tabulated for each galaxy. The
larger galaxies, which tend to have longer and more regular spiral
arms, often have their infrared cores aligned along these arms, with
additional cores in spiral arm spurs. Galaxies without regular spirals
have their cores in more irregular spiral-like filaments, with
typically only one or two cores per filament. Nearly every elongated
emission feature has 8µm cores strung out along its length. The
occurrence of dense cores in long and thin filaments is reminiscent of
filamentary star formation in the solar neighborhood, although on a
scale 100 times larger in galaxies. The cores most likely form by
gravitational instabilities and cloud agglomeration in the filaments.
The simultaneous occurrence of several cores with regular spacings in
some spiral arms suggests that in these cases, all of the cores formed
at about the same time and the corresponding filaments are young.
Total star formation rates for the galaxies correlate with the total
embedded stellar masses in the cores with an average ratio
corresponding to a possible age between 0.2 and 2Myr. This suggests
that the identified cores are the earliest phase for most star
formation.
Description:
Galaxies in the SIRTF Nearby Galaxies Survey (SINGS;
Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K) and Key Insights on Nearby Galaxies: a
Far-Infrared Survey with Herschel (KINGFISH;
Kennicutt+ 2011PASP..123.1347K 2011PASP..123.1347K) surveys plus M83 (NGC 5236) from the
Spitzer Space Telescope archives were selected for low inclination,
large angular size, and diversity of the spiral structure. The
galaxies span Hubble types from Sab through Sm. Spiral arm classes,
which generally correlate with galaxy mass, span the range from
flocculent to multiple arm to grand design.
The post-Basic Calibrated Data (BCD) processed Spitzer images in all
four IRAC bands (3.6, 4.5, 5.8, and 8.0um) and the 24um Multiband
Imaging Photometer (MIPS) images were retrieved.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 15 Galaxies
table2.dat 96 6315 8um cores in the galaxy sample
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See also:
J/ApJ/642/158 : IRAC flux densities in IC2163 and NGC2207 (Elmegreen+, 2006)
J/ApJS/173/538 : XUV-Disk galaxies in the Local Universe (Thilker+, 2007)
J/ApJ/669/493 : Spitzer/Chandra YSOs in Serpens cloud core (Winston+, 2007)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/701/1965 : Radial dust properties of SINGS galaxies (Munoz-Mateos+, 2009)
J/ApJS/190/233 : Spectroscopy & abundances of SINGS galaxies (Moustakas+, 2010)
J/ApJ/745/95 : Herschel FIR & submm photom. of KINGFISH sample (Dale+, 2012)
J/ApJ/757/52 : UV and IR observations for SINGS galaxies. I. (Mao+, 2012)
J/ApJ/767/36 : APEX observations of HOPS protostars (Stutz+, 2013)
J/A+A/552/A19 : Radio-farIR correlation in NGC 6946 (Tabatabaei+, 2013)
J/A+A/576/A33 : KINGFISH galaxy sample radial profile SED (Hunt+, 2015)
J/A+A/616/A78 : Dust extinction map of the Nessie filament (Mattern+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- NGC [628/7793] NGC number
6- 10 F5.2 Mpc Dist [3.3/34.8] Galactic Standard of Reference
distance in Mpc from NED
12- 16 F5.2 mag m-M [27.6/32.7] Distance modulus from NED
18- 20 I3 --- Nc [69/857] Number of chosen cores
22- 37 A16 --- MType Hubble morphological type from NED
39 A1 --- Arm Arm class from Elmegreen & Elmegreen
(1987ApJ...314....3E 1987ApJ...314....3E)
41- 45 F5.2 arcmin R25 [1/11] Radius, R25, in arcmin from NED
47- 51 F5.2 kpc R25kpc [3/28] Radius, R25, in kpc from NED
53- 58 F6.2 pc/arcsec Scale [16.3/168] Parsec scale for one arcsecond
60- 65 F6.3 Msun/yr SFR [0.05/22.8] Star forming rate (1)
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Note (1): SFR are from Hα and 24um in Kennicutt+ (2011PASP..123.1347K 2011PASP..123.1347K)
in all cases but NGC 1566, NGC 2403, NGC 5194, and NGC 5236, where
they are from FUV and total IR in Thilker+ (2007, J/ApJS/173/538).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC Galaxy identifier
10- 11 I2 h RAh Hour of Right Ascension (J2000)
13- 14 I2 min RAm Minute of Right Ascension (J2000)
16- 20 F5.2 s RAs Second of Right Ascension (J2000)
22- 22 A1 --- DE- Sign of the Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000)
34- 38 F5.2 mag 3.6mag [10.7/25.6] Spitzer/IRAC 3.6um band magnitude
40- 44 F5.2 mag e_3.6mag [0.04/55]?=99 Uncertainty in 3.6mag
46- 50 F5.2 mag 4.5mag [10.2/26] Spitzer/IRAC 4.5um band magnitude
52- 56 F5.2 mag e_4.5mag [0.04/45]?=99 Uncertainty in 4.5mag
58- 62 F5.2 mag 5.8mag [9.5/22.7] Spitzer/IRAC 5.8um band magnitude
64- 68 F5.2 mag e_5.8mag [0.05/45.28] Uncertainty in 5.8mag
70- 74 F5.2 mag 8.0mag [7.5/16] Spitzer/IRAC 8.0um band magnitude
76- 79 F4.2 mag e_8.0mag [0.04/4.2] Uncertainty in 8.0mag
81- 85 F5.2 mag 3.6-4.5 [-6.3/5.8] The (3.6-4.5) micron band color
87- 91 F5.2 mag 4.5-5.8 [-2.5/8.7] The (4.5-5.8) micron band color
93- 96 F4.2 mag 5.8-8.0 [0.6/7] The (5.8-8.0) micron band color index
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Mar-2020