J/ApJ/789/81 Multiwavelength survey of HII regions in NGC 300 (Faesi+, 2014)
Molecular cloud-scale star formation in NGC 300.
Faesi C.M., Lada C.J., Forbrich J., Menten K.M., Bouy H.
<Astrophys. J., 789, 81 (2014)>
=2014ApJ...789...81F 2014ApJ...789...81F (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Radio lines ; Photometry, H-alpha ;
Photometry, ultraviolet ; Photometry, infrared ; Extinction ;
Millimetric/submm sources
Keywords: galaxies: individual: NGC 300; galaxies: ISM;
galaxies: star formation; H II regions; stars: formation
Abstract:
We present the results of a galaxy-wide study of molecular gas and
star formation in a sample of 76 H II regions in the nearby spiral
galaxy NGC 300. We have measured the molecular gas at 250pc scales
using pointed CO(J=2-1) observations with the Atacama Pathfinder
Experiment telescope. We detect CO in 42 of our targets, deriving
molecular gas masses ranging from our sensitivity limit of
∼105M☉ to 7x105M☉. We find a clear decline in the CO
detection rate with galactocentric distance, which we attribute
primarily to the decreasing radial metallicity gradient in NGC 300. We
combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24µm,
and Hα narrowband imaging to measure the star formation activity
in our sample. We have developed a new direct modeling approach for
computing star formation rates (SFRs) that utilizes these data and
population synthesis models to derive the masses and ages of the young
stellar clusters associated with each of our H II region targets. We
find a characteristic gas depletion time of 230Myr at 250pc scales in
NGC 300, more similar to the results obtained for Milky Way giant
molecular clouds than the longer (>2Gyr) global depletion times
derived for entire galaxies and kiloparsec-sized regions within them.
This difference is partially due to the fact that our study accounts
for only the gas and stars within the youngest star-forming regions.
We also note a large scatter in the NGC 300 SFR-molecular gas mass
scaling relation that is furthermore consistent with the Milky Way
cloud results. This scatter likely represents real differences in
giant molecular cloud physical properties such as the dense gas
fraction.
Description:
Our sample of star-forming regions in NGC 300 consists of 76 HII
regions from the catalog of Deharveng et al. (1988A&AS...73..407D 1988A&AS...73..407D).
To measure the molecular gas content in our sample of 76 star-forming
regions, we obtained 12CO(J=2-1; rest frequency: 230.538GHz)
observations with the APEX-1 facility heterodyne receiver on the APEX
12m diameter submillimeter telescope. Observations took place over
several epochs between 2011 April 8 and December 16. We obtained over
100hr of observation time divided amongst three project IDs: 13hr
between 2011 May 5 and May 12 under European Southern Observatory
(ESO) project E-087.C-0507A-2011, and the remainder of the time under
Max-Planck-Gesellschaft projects M-087.F-0033-2011 (2011 April 8-18
and June 4-August 7) and M-088.F-0022-2011 (2011 October 10-December
16; PI: J. Forbrich for all three projects).
NGC 300 was observed on 2000 August 5 with the Wide-Field Imager (WFI)
on the Max Planck Gesellschaft/ESO 2.2m telescope at La Silla, Chile,
using the Hα narrowband filter (central wavelength 6588.27Å,
FWHM 74.31Å).
GALEX FUV images were downloaded from the MAST data archive using the
GalexView tool. Observations were taken under the auspices of the
Guest Investigator program GI1_061002 between 2004 October 26 and
December 15, with a total exposure time of 12988s.
NGC 300 was observed with the Spitzer Space Telescope's Multiband
Imaging Photometer for Spitzer (MIPS) on 2004 October 26. BCDs from
AOR 6070016 (PI: G. Helou) were downloaded directly from the Spitzer
Heritage archive.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 59 76 Summary of APEX observations
table3.dat 114 76 Tabulated photometry and results
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See also:
J/ApJ/821/125 : SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016)
J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010)
J/ApJ/723/492 : Physical data of GRS molecular clouds (Roman-Duval+, 20110)
J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009)
J/ApJ/703/1672 : Far-IR and Hα fluxes in galaxies (Kennicutt+, 2009)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)
J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007)
J/AJ/128/1167 : ARAUCARIA project : NGC 300 Cepheids. II (Gieren+, 2004)
J/ApJS/100/125 : CO(J=2-1) Survey of the Milky Way (Sakamoto+, 1995)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- [DCL88] HII region catalog identifier
(Deharveng et al. 1988A&AS...73..407D 1988A&AS...73..407D)
6- 14 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000)
16- 25 F10.6 deg DEdeg Declination in decimal degrees (J2000)
27- 30 F4.1 mK TRMS [5/23] APEX RMS main beam temperature
32- 36 F5.1 km/s vHI [78/197] H I velocity
38- 40 F3.1 kpc RGal [0/7] Deprojected galactocentric distance
42 A1 --- l_ICO Limit flag on ICO
43- 46 I4 mK.km/s ICO [48/1140] Spectrally-integrated CO intensity
48- 50 I3 mK.km/s e_ICO [37/113]? Uncertainty in ICO
52 A1 --- f_ICO [a] a = Gaussian-derived ICO
54- 57 F4.1 km/s W(CO) [2/21]? CO linewidth
59 A1 --- Type Detection type (G1)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- [DCL88] HII region catalog identifier
6 A1 --- l_FHa Limit flag on FHa
7- 12 F6.2 10-17W/m2 FHa [0.5/137]? ESO/WFI Hα flux;
in 1e-14erg/s/cm2
14- 17 F4.2 10-17W/m2 e_FHa [0.2/6]? Uncertainty in FHa
19 A1 --- l_FFUV Limit flag on FFUV
20- 25 F6.1 uJy FFUV [8/5780] GALEX/FUV band flux density
27- 31 F5.1 uJy e_FFUV [2/290]? Uncertainty in FFUV
33 A1 --- l_F24 Limit flag on F24
34- 38 F5.2 mJy F24 [0.01/65] Spitzer/MIPS 24um flux density
40- 43 F4.2 mJy e_F24 [0.02/4.2]? Uncertainty in F24
45- 48 F4.2 mag AHa [0.01/0.7]? Hα extinction
50- 53 F4.2 mag e_AHa [0/0.2]? Uncertainty in AHa
55- 58 F4.2 mag AFUV [0.01/1.6]? FUV extinction
60- 63 F4.2 mag e_AFUV [0.01/0.5]? Uncertainty in AFUV
65 A1 --- l_M(GMCC) Limit flag on M(GMCC)
66- 69 F4.2 10+5Msun M(GMCC) [0.4/7] Giant Molecular Cloud Complex mass
71- 74 F4.2 10+5Msun e_M(GMCC) [0.1/0.7]? Uncertainty in M(GMCC)
76- 79 F4.1 10+3Msun M* [1/38]? Stellar mass
81- 83 F3.1 10+3Msun e_M* [0.2/7]? Uncertainty in M*
85- 87 F3.1 Myr Age [1.8/10]? Age
89- 91 F3.1 Myr e_Age [0.3/4]? Uncertainty in Age
93- 98 E6.1 Msun/yr SFR [0.0002/0.01]? Star Formation Rate
100-105 E6.1 Msun/yr E_SFR [0.0001/0.003]? Upper uncertainty in SFR
107-112 E6.1 Msun/yr e_SFR [0.0001/0.002]? Lower uncertainty in SFR
114 A1 --- Type Detection type (G1)
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Global note:
Note (G1): Detection type as follows:
D = A CO detection source;
M = A marginal CO detection source;
N = A source with CO upper limits.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Jul-2016