J/ApJ/827/33 PHAT. XVI. Star cluster masses and ages (Johnson+, 2016)
Panchromatic Hubble Andromeda Treasury.
XVI. Star cluster formation efficiency and the clustered fraction of
young stars.
Johnson L.C., Seth A.C., Dalcanton J.J., Beerman L.C., Fouesneau M.,
Lewis A.R., Weisz D.R., Williams B.F., Bell E.F., Dolphin A.E.,
Larsen S.S., Sandstrom K., Skillman E.D.
<Astrophys. J., 827, 33-33 (2016)>
=2016ApJ...827...33J 2016ApJ...827...33J (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Clusters, open ; Surveys
Keywords: galaxies: individual: M31; galaxies: star clusters: general
Abstract:
We use the Panchromatic Hubble Andromeda Treasury survey data set to
perform spatially resolved measurements of star cluster formation
efficiency (Γ), the fraction of stellar mass formed in
long-lived star clusters. We use robust star formation history and
cluster parameter constraints, obtained through color-magnitude
diagram analysis of resolved stellar populations, to study Andromeda's
cluster and field populations over the last ∼300Myr. We measure
Γ of 4%-8% for young, 10-100Myr-old populations in M31. We find
that cluster formation efficiency varies systematically across the M31
disk, consistent with variations in mid-plane pressure. These Γ
measurements expand the range of well-studied galactic environments,
providing precise constraints in an HI-dominated, low-intensity star
formation environment. Spatially resolved results from M31 are broadly
consistent with previous trends observed on galaxy-integrated scales,
where Γ increases with increasing star formation rate surface
density (ΣSFR). However, we can explain observed scatter in
the relation and attain better agreement between observations and
theoretical models if we account for environmental variations in gas
depletion time (τdep) when modeling Γ, accounting for the
qualitative shift in star formation behavior when transitioning from a
H2-dominated to a HI-dominated interstellar medium. We also
demonstrate that Γ measurements in high ΣSFR starburst
systems are well-explained by τdep-dependent fiducial Γ
models.
Description:
The Panchromatic Hubble Andromeda Treasury (PHAT) survey imaged 1/3 of
the disk of M31 in six passbands spanning near-ultraviolet to
near-infrared wavelengths. The survey provides resolved stellar
photometry of 117 million sources that we use to determine the
properties of both the cluster and field populations, with
completeness limits that allow the detection of individual MS stars
down to ∼3M☉. Here we provide an overview of the crowded field
stellar photometry derived for PHAT; full details are found in
Dalcanton+ (2012ApJS..200...18D 2012ApJS..200...18D) and Williams+ (2014, J/ApJS/215/9).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 35 1249 Cluster fitting results
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See also:
J/MNRAS/451/724 : PHAT. XIII. M31 Cepheid P-L relation (Wagner-Kaiser+, 2015)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJ/758/133 : Metallicity profile of M31 HII regions and PNe (Sanders+, 2012)
J/ApJ/752/95 : PHAT stellar cluster survey. I. Year 1 (Johnson+, 2012)
J/A+A/529/A25 : Photom. of star clusters in 5 nearby gal. (Silva-Villa+, 2011)
J/AJ/140/1194 : FUV/HI relations in nearby galaxies (Bigiel+, 2010)
J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)
J/ApJ/762/123 : PHAT. IV. Initial Mass Function (Weisz+, 2013)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- APID [2/6182] Cluster Identification Number (1)
7- 8 A2 --- RegID Region Identification (2)
10- 12 F3.1 [yr] logAge [7/9] Best Log Age
14- 16 F3.1 [yr] b_logAge [6.6/8.4] 16th Percentile log Age
18- 20 F3.1 [yr] B_logAge [7/9.6] 84th Percentile log Age
22- 25 F4.2 [Msun] logMass [2.2/4.4] Best Log Mass
27- 30 F4.2 [Msun] b_logMass [0/4.3] 16th Percentile log Mass
32- 35 F4.2 [Msun] B_logMass [2.3/5] 84th Percentile log Mass
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Note (1): From Andromeda Project, Johnson et al. (2015, J/ApJ/802/127).
Note (2): Clusters with NA do not lie within any of the analysis regions.
To measure Γ and investigate its variation across the disk of
M31, we divide the PHAT survey footprint into seven regions. These
regions were defined to isolate the 10kpc star-forming ring (Region 2)
from the inner disk (Region 1; Rgc<10kpc) and outer disk (Region 3;
Rgc>13kpc), and divide the mass formed over the 10-100Myr age range
into approximately equal amounts. See section 2.2 for further
explanations.
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History:
From electronic version of the journal
References:
Dalcanton et al. 2012ApJS..200...18D 2012ApJS..200...18D
Rosenfield et al. Paper I 2012ApJ...755..131R 2012ApJ...755..131R
Williams et al. Paper II 2012ApJ...759...46W 2012ApJ...759...46W
Beerman et al. Paper III 2012ApJ...760..104B 2012ApJ...760..104B
Weisz et al. Paper IV 2013ApJ...762..123W 2013ApJ...762..123W Cat. J/ApJ/762/123
Fouesneau et al. Paper V 2014ApJ...786..117F 2014ApJ...786..117F
Simones et al. Paper VI 2014ApJ...788...12S 2014ApJ...788...12S
Dong et al. Paper VII 2014ApJ...785..136D 2014ApJ...785..136D
Dalcanton et al. Paper VIII 2015ApJ...814....3D 2015ApJ...814....3D
Veyette et al. Paper IX 2014ApJ...792..121V 2014ApJ...792..121V
Williams et al. Paper X 2014ApJS..215....9W 2014ApJS..215....9W Cat. J/ApJS/215/9
Lewis et al. Paper XI 2015ApJ...805..183L 2015ApJ...805..183L
Gregersen et al. Paper XII 2015AJ....150..189G 2015AJ....150..189G
Wagner-Kaiser et al. Paper XIII 2015MNRAS.451..724W 2015MNRAS.451..724W Cat. J/MNRAS/451/724
Senchyna et al. Paper XIV 2015ApJ...813...31S 2015ApJ...813...31S
Gordon et al. Paper XV 2016ApJ...826..104G 2016ApJ...826..104G
Johnson et al. Paper XVI 2016ApJ...827...33J 2016ApJ...827...33J This catalog
Lewis et al. Paper XVII 2017ApJ...834...70L 2017ApJ...834...70L
Johnson et al. Paper XVIII 2017ApJ...839...78J 2017ApJ...839...78J
Williams et al. Paper XIX 2017ApJ...846..145W 2017ApJ...846..145W Cat. J/ApJ/846/145
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Nov-2016