J/ApJ/895/71 8um Cores in NGC 891, NGC 3628 and IC 5052 (Elmegreen+, 2020)
Observing the Earliest Stages of Star Formation in Galaxies: 8um cores in three
edge-on disks
Elmegreen B.G., Elmegreen D.M.
<Astrophys. J., 895, 71 (2020)>
=2020ApJ...895...71E 2020ApJ...895...71E
ADC_Keywords: Galaxies; Star Forming Region; Photometry, infrared
Keywords: Disk galaxies ; Spiral galaxies ; Star formation ;
Star forming regions ; Young star clusters ; Interstellar emissions
Abstract:
To study the vertical distribution of the earliest stages of star
formation in galaxies, three edge-on spirals, NGC891, NGC3628, and
IC5052, observed by the Spitzer Space Telescope InfraRed Array Camera
(IRAC) were examined for compact 8µm cores using an unsharp mask
technique; 173, 267, and 60 cores were distinguished, respectively.
Color-color distributions suggest a mixture of polycyclic aromatic
hydrocarbons and highly extincted photospheric emission from young
stars. The average V-band extinction is ∼20mag, equally divided
between foreground and core. IRAC magnitudes for the clumps are
converted to stellar masses assuming an age of 1Myr, which is about
equal to the ratio of the total core mass to the star formation rate
in each galaxy. The extinction and stellar mass suggest an intrinsic
core radius of ∼18pc for 5% star formation efficiency. The
half-thickness of the disk of 8µm cores is 105pc for NGC891 and
74pc for IC5052, varying with radius by a factor of ∼2. For NGC3628,
which is interacting, the half-thickness is 438pc, but even with this
interaction, the 8µm disk is remarkably flat, suggesting vertical
stability. Small-scale structures like shingles or spirals are seen in
the core positions. Very few of the 8µm cores have optical
counterparts.
Description:
To find edge-on galaxies for this survey, we searched the Spitzer
archives for InfraRed Array Camera (IRAC) channel 4 (8µm)
observations using galaxy samples designed for studies of thick disks.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 93 500 8um Cores in NGC 891, NGC 3628 and IC 5052
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See also:
VII/74 : Atlas of Peculiar Galaxies (Arp 1966)
J/ApJ/642/158 : IRAC flux densities in IC2163 and NGC2207 (Elmegreen+, 2006)
J/ApJ/669/493 : Spitzer/Chandra YSOs in Serpens cloud core (Winston+, 2007)
J/ApJ/688/237 : Disk corrugations in IC 2233 (Matthews+, 2008)
J/AJ/135/693 : X-ray and IR sources in RCW 108 (Wolk+, 2008)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/140/266 : NGC 1333 X-ray luminous YSOs properties (Winston+, 2010)
J/A+A/527/A109 : Dust and PAH emission SEDs of disk galaxies (Popescu+, 2011)
J/ApJ/767/36 : APEX observations of HOPS protostars (Stutz+, 2013)
J/AJ/146/86 : Cosmicflows-2 catalog (Tully+, 2013)
J/A+A/565/A4 : NGC 891 70-500um images (Hughes+, 2014)
J/ApJ/862/25 : Hα&UV emission scale heights for edge-on gal. (Jo+,2018)
J/ApJS/245/14 : 8um cores in spiral arms of nearby galaxies (Elmegreen+, 2019)
J/ApJ/882/5 : ALMA data 5 luminous & ultraluminous IR gal. (Wilson+, 2019)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID Galaxy identification
10- 11 I2 h RAh [2/20] 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 mag3.6 [13.2/20.3]? Spitzer/IRAC 3.6micron band
magnitude (1)
40- 43 F4.2 mag e_mag3.6 [0.1/3]? Uncertainty in mag3.6
45- 49 F5.2 mag mag4.5 [12.3/19.7]? Spitzer/IRAC 4.5 micron band
magnitude (1)
51- 54 F4.2 mag e_mag4.5 [0.1/3]? Uncertainty in mag4.5
56- 60 F5.2 mag mag5.8 [11.1/19]? Spitzer/IRAC 5.8micron band magnitude
(1)
62- 65 F4.2 mag e_mag5.8 [0.09/3]? Uncertainty in mag5.8
67- 71 F5.2 mag mag8.0 [9.3/17.8] Spitzer/IRAC 8.0micron band magnitude
(1)
73- 76 F4.2 mag e_mag8.0 [0.06/3] Uncertainty in mag8.0
78- 82 F5.2 mag 3.6-4.5 [-1.2/2.2]? Color, [3.6]-[4.5]
84- 88 F5.2 mag 4.5-5.8 [-0.7/3.93]? Color, [4.5]-[5.8]
90- 93 F4.2 mag 5.8-8.0 [0.51/3.08]? Color, [5.8]-[8.0]
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Note (1): Magnitudes in the Vega scale
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 20-Sep-2021