Context :

Aims : The SOLIS ( Seeds Of Life In Space ) IRAM/NOEMA Large Program aims at studying a set of crucial complex organic molecules in a sample of sources , with well-known physical structure , covering the various phases of Solar-type star formation .
One representative object of the transition from the prestellar core to the protostar phases has been observed toward the Very Low Luminosity Object ( VeLLO ) called L1521F .
This type of source is important to study to make the link between prestellar cores and Class 0 sources and also to constrain the chemical evolution during the process of star formation .

Methods : Two frequency windows ( 81.6–82.6 GHz and 96.65–97.65 GHz ) were used to observe the emission from several complex organics toward the L1521F VeLLO .
These set-ups cover transitions of ketene ( H _ { 2 } CCO ) , propyne ( CH _ { 3 } CCH ) , formamide ( NH _ { 2 } CHO ) , methoxy ( CH _ { 3 } O ) , methanol ( CH _ { 3 } OH ) , dimethyl ether ( CH _ { 3 } OCH _ { 3 } ) and methyl formate ( HCOOCH _ { 3 } ) .

Results : Only 2 transitions of methanol ( A ^ { + } , E _ { 2 } ) have been detected in the narrow window centered at 96.7 GHz ( with an upper limit on E _ { 1 } ) in a very compact emission blob ( \sim 7 ^ { \prime \prime } corresponding to \sim 1000 au ) toward the North-East of the L1521F protostar .
The CS 2–1 transition is also detected within the WideX bandwidth .
Consistently , with what has been found in prestellar cores , the methanol emission appears \sim 1000 au away from the dust peak .
The location of the methanol blob coincides with one of the filaments previously reported in the literature .
The excitation temperature of the gas inferred from methanol is ( 10 \pm 2 ) K , while the H _ { 2 } gas density ( estimated from the detected CS 2–1 emission and previous CS 5–4 ALMA observations ) is a factor > 25 higher than the density in the surrounding environment ( n ( H _ { 2 } ) \geq 10 ^ { 7 } cm ^ { -3 } ) .

Conclusions : From its compactness , low excitation temperature and high gas density , we suggest that the methanol emission detected with NOEMA is i ) either a cold and dense shock-induced blob , recently formed ( \leq few hundred years ) by infalling gas or ii ) a cold and dense fragment that may have just been formed as a result of the intense gas dynamics found within the L1521F VeLLO system .