A deep Parkes H i survey of the Sculptor group and filament: H i mass function and environment

Abstract

We present the results of a deep survey of the nearby Sculptor group and the associated Sculptor filament taken with the Parkes 64-m radio telescope in the 21-cm emission line of neutral hydrogen. We detect 31 H I sources in the Sculptor group/filament, eight of which are new H I detections. We derive a slope of the H I mass function along the Sculptor filament of α = −1.10 +0.20 −0.11 , which is significantly flatter than the global mass function and consistent with the flat slopes previously found in other low-density group environments. Some physical process, such as star formation, photoionisation or ram-pressure stripping, must therefore be responsible for removing neutral gas predominantly from low-mass galaxies. All of our H I detections have a confirmed or tentative optical counterpart and are likely associated with luminous rather than 'dark' galaxies. Despite a column density sensitivity of about 4 × 10 17 cm −2 , we do not find any traces of extragalactic gas or tidal streams, suggesting that the Sculptor filament is, at the current time, a relatively quiescent environment that has not seen any recent major interactions or mergers.

The ALFALFA H i mass function: a dichotomy in the low-mass slope and a locally suppressed ‘knee’ mass

“…Studies of the HIMF in individual groups (e.g. Verheijen et al 2001;Kovac et al 2005;Freeland et al 2009;Kilborn et al 2009;Pisano et al 2011;Westmeier et al 2017) have generally found that they have approximately flat (α = −1) low-mass slopes, with the notable exceptions of Stierwalt et al (2009) and Davies et al (2011), both of which found very steep (α < −1.4) low-mass slopes in the Leo region and across various groups within the AGES footprint, respectively. These results are apparently in tension with those of ALFALFA and HIPASS, which measured a steeper slope (α ∼ −1.3) and do not find a flattening of the slope in higher density regions (Zwaan et al 2005;Martin et al 2010;Moorman et al 2014;Jones et al 2016).…”

The H i mass function of group galaxies in the ALFALFA survey

“…In addition to blind measurements of the HIMF over wide fields (Zwaan et al 1997;Rosenberg & Schneider 2002;Zwaan et al 2003Zwaan et al , 2005Martin et al 2010;Jones et al 2018;Said et al 2019), there have been a number of measurements E-mail: mjones@iaa.es † E-mail: hess@astro.rug.nl of the HIMF in specific galaxy groups (Verheijen et al 2001;Kovac et al 2005;Freeland et al 2009;Kilborn et al 2009;Stierwalt et al 2009;Davies et al 2011;Pisano et al 2011;Westmeier et al 2017). While the former have shown that the HIMF in the local Universe follows a Schechter function (Schechter 1976) shape (a declining power law with increasing H i mass that is truncated by an exponential decay at the 'knee' mass) with a low-mass slope parameter, α, of approximately -1.3 and a 'knee' mass just below 10 10 M , the latter studies have almost universally found the low-mass slope in galaxy groups to be flat (α ≈ −1) down to about log M H i /M ∼ 7.…”

Eddington's demon: inferring galaxy mass functions and other distributions from uncertain data

“…xmax =9.5)To add the reference H i MFs of the HIPASS(Zwaan et al 2005) and ALFALFA(Martin et al 2010) surveys, use x = c ( survey$grid$x ) y = dfmodel (x , c ( log10 (6.0 e -3) ,9.80 , -1.37)) lines (10^x ,y , lty =2 , lwd =1.5 , col =" blue ") y = dfmodel (x , c ( log10 (4.8 e -3) ,9.96 , -1.33) lines (10^x , y ) , lty =4 , lwd =1.5 , col ="#00 bb00 ")InFig. E2, the Sculptor H i MF clearly differs from the mean H i MF in the local universe, as discussed byWestmeier et al (2017). The best-fitting parameters are displayed viadfwrite ( survey ) resulting in the output dN /( dVdx ) = log (10)*10^p [1]* mu^( p [3]+1) * exp ( -mu ) , where mu =10^( x -p [2…”

“…The chosen graphical arguments display the fitting function in red, display the observed data in black, remove posterior data, suppress the effective volume line and adjust the binning of input data. Note that there are marginal differences to the uncertainty ranges quoted by Westmeier et al (2017) due to a difference in the bootstrapping technique used in the previous (parametric bootstrapping) and the current (non-parametric bootstrapping) version of dftools.…”