Salvatore di Giacomo e Giovanni Laterza. Descrizione di un carteggio inedito

Il saggio prende in analisi un corposo scambio epistolare inedito tra Salvatore di Giacomo e Giovanni Laterza risalente al periodo 1902-1924. La sezione principale del carteggio riguarda il lavoro di edizione e di composizione della raccolta di novelle Nella vita, apparsa nella collana “Opere varie” nel 1903. La raccolta, proposta da Benedetto Croce, rientra in una serie di pubblicazioni d’inizio Novecento che attesta un iniziale interesse della Casa editrice per le pubblicazioni di narrativa

The CHESS survey of the L1157-B1 shock: the dissociative jet shock as revealed by Herschel--PACS

Outflows generated by protostars heavily affect the kinematics and chemistry of the hosting molecular cloud through strong shocks that enhance the abundance of some molecules. L1157 is the prototype of chemically active outflows, and a strong shock, called B1, is taking place in its blue lobe between the precessing jet and the hosting cloud. We present the Herschel-PACS 55--210 micron spectra of the L1157-B1 shock, showing emission lines from CO, H2O, OH, and [OI]. The spatial resolution of the PACS spectrometer allows us to map the warm gas traced by far-infrared (FIR) lines with unprecedented detail. The rotational diagram of the high-Jup CO lines indicates high-excitation conditions (Tex ~ 210 +/- 10 K). We used a radiative transfer code to model the hot CO gas emission observed with PACS and in the CO (13-12) and (10-9) lines measured by Herschel-HIFI. We derive 20010^5 cm-3. The CO emission comes from a region of about 7 arcsec located at the rear of the bow shock where the [OI] and OH emission also originate. Comparison with shock models shows that the bright [OI] and OH emissions trace a dissociative J-type shock, which is also supported by a previous detection of [FeII] at the same position. The inferred mass-flux is consistent with the "reverse" shock where the jet is impacting on the L1157-B1 bow shock. The same shock may contribute significantly to the high-Jup CO emission.Comment: 7 pages, 9 figures, accepted for publication in Astronomy and Astrophysic

Da Per sempre ragazzo a Future: Le antologie della "speranza" dopo il trauma del G8

In questo contributo si vuole indagare da un’ottica transgenerazionale e transnazionale il nesso memoria-attivismo in due antologie -- Per sempre ragazzo (2011) e Future (2019) -- prodotte in momenti storici diversi, che rappresentano soggettività politiche diverse, e la cui futuribilità sembra essere condizionata da una genealogia storica diversa. Con l’aiuto della distinzione fatta da Ann Rigney 52018, 2020) tra trauma, speranza e indignazione da un lato, e tra “memory activism” e “memory in activism” dall’altro, si cerca di determinare fino a che punto questi prodotti culturali riescono a veicolare una memoria culturale sia traumatica che propositiva di ciò che in ambedue i casi viene individuato come un’ingiustizia sociale

Strong H₂O and high-<i>J</i> CO emission towards the Class 0 protostar L1448-mm

The spectrum of the Class 0 source L1448-mm has been measured over the wavelength range extending from 6 to 190 μm with the Long Wavelength Spectrometer (LWS) and the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). The far infrared spectrum is dominated by strong emission from gaseous H2O and from CO transitions with rotational quantum numbers J ≥ 14; in addition, the H2 pure rotational lines S(3), S(4) and S(5), the OH fundamental line at 119 μm, as well as emission from [O I]63 μm and [C II] 158 μm are also observed. The strong CO and water emission can be consistently explained as originating in a warm gas component at T ~ 700-1400 K and nH2~(3-50) 104cm-3 , which fills about 0.2-2% of the ~ 75" LWS field of view (corresponding, assuming a single emitting region, to a physical size of about (3-12)" or (0.5-2) 10-2 pc at d = 300 pc). We derive an H2O/CO abundance ratio ~ 5, which, assuming a standard CO/H2 abundance of 10-4, corresponds to H2O/H2 ~ 5 10-4. This value implies that water is enhanced by about a factor ~ 103 with respect to its expected abundance in the ambient gas. This is consistent with models of warm shocked regions which predict that most of the free atomic oxygen will be rapidly converted into water once the temperature of the post-shocked gas exceeds ~ 300 K. The relatively high density and compact size inferred for this emission may suggest an origin in the shocked region along the molecular jet traced by SiO and EHV CO millimeter line emission. Further support is given by the fact that the observed enhancement in H2O can be explained by shock conditions similar to those expected to produce the abundant SiO observed in the region. L1448-mm shows the largest water abundance so far observed by ISO amongst young sources displaying outflow activity; we argue that the occurrence of multiple shocks over a relatively short interval of time, like that evidenced in the surroundings of L1448-mm, could have contributed to enrich the molecular jet with a high H2O column density

The CHESS survey of the L1157-B1 bow-shock: high and low excitation water vapor

Molecular outflows powered by young protostars strongly affect the kinematics and chemistry of the natal molecular cloud through strong shocks resulting in substantial modifications of the abundance of several species. As part of the "Chemical Herschel Surveys of Star forming regions" guaranteed time key program, we aim at investigating the physical and chemical conditions of H20 in the brightest shock region B1 of the L1157 molecular outflow. We observed several ortho- and para-H2O transitions using HIFI and PACS instruments on board Herschel, providing a detailed picture of the kinematics and spatial distribution of the gas. We performed a LVG analysis to derive the physical conditions of H2O shocked material, and ultimately obtain its abundance. We detected 13 H2O lines probing a wide range of excitation conditions. PACS maps reveal that H2O traces weak and extended emission associated with the outflow identified also with HIFI in the o-H2O line at 556.9 GHz, and a compact (~10") bright, higher-excitation region. The LVG analysis of H2O lines in the bow-shock show the presence of two gas components with different excitation conditions: a warm (Tkin~200-300 K) and dense (n(H2)~(1-3)x10^6 cm-3) component with an assumed extent of 10" and a compact (~2"-5") and hot, tenuous (Tkin~900-1400 K, n(H2)~10^3-10^4 cm-3) gas component, which is needed to account for the line fluxes of high Eu transitions. The fractional abundance of the warm and hot H2O gas components is estimated to be (0.7-2)x10^{-6} and (1-3)x10^{-4}, respectively. Finally, we identified an additional component in absorption in the HIFI spectra of H2O lines connecting with the ground state level, probably arising from the photodesorption of icy mantles of a water-enriched layer at the edges of the cloud.Comment: Accepted for publication in A&A. 12 pages, 9 figures, 4 table

Looking at the photon-dominated region in NGC 2024 through FIR line emission

We present the ISO-LWS spectra (45-200 μm) of both the molecular cloud NGC 2024 and its associated HII region. We observed the two Class 0 objects FIR3 and FIR5 and the infrared source IRS2. All the spectra appear quite similar, with approximately the same strength high-J CO rotational lines (from Jup=17 to Jup=14), and atomic and ionic lines from oxygen, carbon and nitrogen. This uniformity suggests the bulk of the emission is from the extended cloud, and is not related to the local source conditions. The molecular emission has been modelled with a large velocity gradient (LVG) code, and the results imply that the emission originates in a clumpy, extended PDR with a temperature T ~ 100 K and a density nH2 ~ 106 cm-3. CO column densities in excess of 1018 cm-2 are derived for this molecular component. A line intensity ratio I([O I] 63 μm)/I([O I] 145 μm) of about 5 is found through all the region, indicating either that these two lines are both optically thick at the same temperature of CO, or, more likely, that the 63 μm line is strongly absorbed by cold foreground gas. The ionised emission lines have been consistently modelled with CLOUDY; the lines arise from gas illuminated by an O9.5 star or its UV equivalent, representing the ionising capability of the whole OB cluster present in the region. From the intensity ratios of the ionic lines, relevant physical properties of the ionised gas (N/O abundance, electron density) are derived

ISO observations of the HH 24-26 regions

We report the results of an investigation, performed with the Long Wavelength Spectrometer (LWS) and the Short Wavelength Spectrometer (SWS) on-board the ISO satellite, on the star forming region associated with the Herbig-Haro objects HH24-25 and 26. In particular, we obtained low-resolution LWS spectra towards the two Class 0 sources HH24MMS and HH25MMS as well as towards the Class I source HH26IR and its associated flow. In addition, SWS scans of pure H2 rotational lines in HH24MMS where acquired. All the spectra present the [OI] 63 μm and the [CII] 158 μm lines, while significant molecular emission from CO and H2O is detected only from HH25MMS and along the blue lobe of the HH26IR outflow, where the shocked activity is also evidenced by the presence of strong near infrared knots. The physical conditions of the regions strongly emitting in molecular lines are derived, showing that the two Class 0 sources are characterised by lower temperatures and higher densities than the HH26IR flow. The presence of both J and C shocks are envisaged to take into account the observed emission

Molecular line emissions from pre main sequence objects

We present some preliminary results obtained with the LWS G.T. programme on the study of young objects driving molecular outflows. In particular, we discuss the importance of molecular emission in these sources and address the role of the H20 cooling

ISO-LWS study of pre-main sequence sources

We present the results obtained with the ISO Long Wavelength Spectrometer on a sample of Pre-MS sources, where several molecular lines of CO, H2O and OH have been detected. The analysis of the CO lines indicates that gas temperatures as low as 200 K are consistent with the data. This would be in agreement with the relatively low abundance of water in the gas phase measured in most of the objects