Constraining the star formation rate in the solar neighbourhood with star clusters

Abstract

This paper investigates the star formation rate (SFR) in the solar neighbourhood. First, we build the local age distribution function (ADF) with an updated sample of 442 star clusters located at less than 1 kpc from the Sun. Next, we define the SFR, compute the individual mass evolution of a population of artificial clusters covering the broad range of parameters observed in actual clusters, and assume 100 M⊙ as the low‐mass limit for effective cluster observation. This leads to a simulated ADF, which is compared to the low‐noise solar neighbourhood ADF. The best match corresponds to a non‐constant SFR presenting two conspicuous excesses for ages ≤9 Myr and between 220–600 Myr (the local starburst). The average SFR is , corresponding to the average surface SFR . These values are consistent with the SFR inferred from embedded clusters (ECs), but much lower (≲16 per cent) than that implied by field stars. Both the local starburst and the recent star formation period require to be described. The simulations show that 91.2 ± 2.7 per cent of the clusters created in the solar neighbourhood do not survive the first 10 Myr, which is consistent with the rate of EC dissolution.

Anchors for the cosmic distance scale: the Cepheid QZ Normae in the open cluster NGC 6067

“…The counts do not level-off sharply, which may indicate the breadth of the cluster's coronal region (Kholopov 1969) and its dissolution into the field. Most star clusters dissolve into the field relatively rapidly, and don't survive well beyond 10 Myr (e.g., disruption by Galactic tides, Lada & Lada 2003;Bonatto & Bica 2011). Clusters reaching the age of NGC 6067 are thus rare.…”

Discovering protostars and their host clusters via WISE

“…A detailed characterization of individual YSOs (SED modelling, Robitaille et al 2007) and protoclusters shall await additional observations (e.g., ALMA), and will be pursued elsewhere. Ultimately, the results will bolster the statistics linked to supporting new theories of star-formation (e.g., the 'fireworks hypothesis', Koenig et al 2012), and constraining parameters such as the star formation rate and local starburst history (e.g., Bonatto & Bica 2011 A JHK s color-color diagram ( Fig. 1) is compiled for the YSO candidates highlighted by Doppmann et al (2005), Robitaille et al (2008), Gutermuth et al (2010), Straižys & Kazlauskas (2010), Majaess et al (2012), andRosvick et al (2012, in prep) 3 .…”

“…1), cluster dissolution timescale ('infant mortality rate' for protoclusters, Lada & Lada 2003), and the Galaxy's spiral structure. Bonatto & Bica (2011) examined newly identified clusters (e.g., Bica et al 2003) and inferred that the local star formation rate is not constant and is punctuated for τ ≤ 9 and 220-600 Myr, while Spitzer legacy results for five nearby protostar-hosting complexes imply that a sizable fraction of the YSOs lie in loose clusters (n > 35, ρ > 1M ⊙ /pc 3 , Evans et al 2009). Such pertinent determinations may be invariably strengthened by increasing the statistics of known protostars and protoclusters.…”

“…Identifying young stellar objects (YSOs) and their host clusters bolsters efforts to constrain the star formation rate, local starburst history (Bonatto & Bica 2011, their Fig. 1), cluster dissolution timescale ('infant mortality rate' for protoclusters, Lada & Lada 2003), and the Galaxy's spiral structure.…”

Extracting parameters from colour–magnitude diagrams

“…Lada & Lada 2003;Goodwin & Bastian 2006), star-formation rate in the Galaxy (e.g. Lamers & Gieles 2006;Bonatto & Bica 2011), among others. This kind of analysis started with Trumpler (1930) and continues to date (e.g.…”